Dear Google Answers:

I would like a precise definition of what is a color.  For example,
what is "brown"?  How would I measure if a certain object is "brown"? 
If a contract says that a particular item must be, say, "red".  How
can it be shown legally that the contract has been (or not) met?

A good answer should explain to me how I can measure (e.g., with RGB
code) and determine if an object is the stated color.  Possibly there 
are well recognized ranges of RGB codes for each named color?

Thanks!

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Request for Question Clarification by hammer-ga on 05 Jan 2005 09:23 PST

Ken13,

What kind of object are we talking about? Are we talking about a
physical item, like a life jacket? Or are we talking about an image on
a computer screen? RGB would only apply for emitted light. A printed
image would use CMYK. A painted object is RYB. Etc...

- Hammer

---

Clarification of Question by ken13-ga on 05 Jan 2005 10:11 PST

Thank you for your interest in answering me question.

The object is a door.  Neighborhood code says the door must be
"brown".  How do I know what is "brown"?  When does "brown" become
"red"?   I rather think there must be a scientific answer to - a way
to measure - what is a color.  Perhaps my question is also legalese if
the scientific community does not define colors, but only measures of
color, say, RGB.

I can take a picture of the door with a digital camara and then get
RGB values of the JPEG image with, say, Microsoft PhotoEditor.  I am
aware that a picture might not have true color fidelity.  Take RGB =
138,10,34.  Is this brown?  Red?  Or some other color?

Hi Kent
         I read all the comments, and while they contain interesting
tidbits, none of them provides an answer on scientific definition and
standard lists of colors.
 Since you kept the question open, an physics-based answer seems to be
in oder.  It is an interesting topic and Feynman devotes whole chapter
to it in his famous "The Feynman Lectures on Physics : (Vol 1)"
http://www.amasci.com/feynman.html  

He talk not only about human vision, but also about animals, like buterflies,
who see many flowers which we, humans, percieve as white to be 'brightly colored'.

So, there are several meanings of the common word color:

1) Spectrum (of frequencies) of light (or in general emg radiation)
comming to the eye (or other sensor). Only part of that spectrum is
visible and that
visible portion is called 'light'. It is shown here:
 http://en.wikipedia.org/wiki/Visible_light

The picture of prism (in the reference above) is the simplest
representation of the concept of 'spectrum'. It is distributions of
energies (or frequencies or wavelengths or wavenumbers). That is
dependence of intensity on this one physical quantity which determines
the wavelength of the radiation.

2) Trichromat defines color we see. "We" means humans. Even though everyone 
may have different subjective reaction to a given spectrum, most of us have the
same three chromatic and one B/W type of receptors (cones and rods)
which define the subjective color - color as it is recieved by visual
cortex of the brain.
http://en.wikipedia.org/wiki/Trichromatic     

The 'white' and 'brown' are defined at this level. They are composite colors,
rather then 'spectral colors'. This is explained here:
http://acept.la.asu.edu/PiN/rdg/color/composition.shtml

Figures A B C shows spectra, which all 'look pink' to an average human
- and so have same trichromatic coefficients. Same for brown and white
(color od sun,
also called daylight). The three coefficients -Redness-greenness-
coordinates  of subjective color space can be represented in
different, eqivalent ways (Hunter L,a,b or CIELAB)..
http://www.color-tec.com/1gloss.htm

These representations are used in the industry and different
industries have different standards. Here is an article on shades of
'brown':
".. CS was significantly correlated with the measured lightness (L*)
and with the yellow chromaticity coordinate (b*) of the underfur
samples.."
http://taylorandfrancis.metapress.com/app/home/contribution.asp?wasp=bn42d3kqtl6kwmebyddj&referrer=parent&backto=issue,2,7;journal,19,23;linkingpublicationresults,1:103274,1


3) These are not same is RGB or equivalnet HLS representation of a
SUBSET of the color space - a subset which can be created using 3
phosphors of a typical CRT tube. Similar issue is 'printing' with
given number of color inks, explained here:
http://www.cis.rit.edu/mcsl/research/PDFs/Report.pdf
CRT colors
http://stuffo.howstuffworks.com/tv3.htm

Again, different industries use different systems. There are some
common names and  universal standards for names ":National Bureau of
Standards (US) lists 267 color names.."
http://www.psych.ndsu.nodak.edu/mccourt/Psy460/Color Vision/Color Vision.html
 Munsell chips are practical standard for the printing industry.
http://www.cis.rit.edu/mcsl/research/PDFs/Berns_art_digitize_lowres.pdf

 Martha Stuart is still setting standards in decorating industry: 
"in addition to these 1,000 shades, Sherwin Williams will premiere the
Martha Stewart Signature(TM) Color Palette, a Decorating System of 416
colors and 39 coordinating color palettes, each personally selected by
Martha to reflect her taste and personal decorating style .."
http://www.specialchem4coatings.com/news-trends/displaynews.aspx?id=490
http://www.specialchem4coatings.com/news-trends/displaynews.aspx?id=490

4) So far, we talked about light entering the eye.
 Color of an object is a diffrent kettle of fish. It is a transformation of the
 incoming spectrum (illumination) to the reflected spectrum (or transmitted
light spectrum). It is quite complex and really too much for a dispute
about the door, except to note that source of light in that area  has 
effect on percieved color.

5) Practical solution called for is to accept apropriate industry standard:
  which means: to go to a paint store and get bunch of the color strips.
The whole book of strips sells for $20 in the US.
 Then compare strip to the door; find a match in several illumination
typical for that space (evening, daylight..).

http://www.ivillage.com/home/experts/homeclin/articles/0,,249850_249930,00.html?arrivalSA=1&cobrandRef=0&arrival_freqCap=1&pba=adid=13269340

 IN CONCLUSION : if you find a good match, on the brown strip or swatch,
 in at least one typical ilumination, then the doors are brown.


6) It can be made more complicated, of course (if you are a defendant :-) 
The number of color receptors being three has been disputed:
http://www.rmki.kfki.hu/~lukacs/TETRACH.htm

 Introduce some psychology and philosophy:

 "..all researchers publishing on colour naming,
 categorization or vision accept one or more of the four hypotheses; 

there are no mechanisms concerned with colour vision; 

in English more than four colour names are needed to describe the
character of bright colour viewed in a dark surround ;

relativism and unconstrained plasticity should prevail; the right
approach is hermeneutics and/or social constructivism  .."
===========         =====================  
http://www.bbsonline.org/Preprints/OldArchive/bbs.saunders.html

Feel free to ask for clarifications. When all is clear, rating is appreciated.
 Hegie

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Clarification of Answer by hedgie-ga on 13 Jan 2005 23:09 PST

Thank you for the rating Kent.

The color brown is usually defined be decimal RGB as 165-42-42

as illustrated e.g. here
------------------------------
The color brown is defined here by 127 units of red and 47 units of
green or RGB=127-47-0
http://www.yorku.ca/eye/brown.htm

 On "Extended" Named Colors  brown=A52A2A = 165-42-42
http://www.utoronto.ca/ian/books/xhtml1/appd/color2.html

and on  #10 in X- color list of 85 colors
 10 brown 0.647 0.165 0.165 = 165-42-42
http://cubit.sandia.gov/help-version9.1/Appendix/X-Windows_Colors.html
------------------------
 
 However, I have been thinking about this part of your question, which
remained unanswerd:
 
" where does the brown ends and red starts"?

which remained unanswered. I looked again to see if someone proposed
decomposition of the color space into small areas (polygons) around
each named color.

I did not find any, and so, to answer your question, I am proposing the following
decomposition using an X-colorlist and Voronoi diagrams. This prescription assigns 
a name to all colors in the RGB subsapce.


Select a colorlist
 http://en.wikipedia.org/wiki/Web_colors
 
 Recommended is X-windows colorlist
 http://www.mcfedries.com/CreatingAWebPage/x11colors.asp
 
 Apply  Voronoi Tesselation to points which represent these colors on the
 CIE 1931 chromaticity diagram
 http://en.wikipedia.org/wiki/Color
 
 Each polygon contains point which are entitled to the name of the central point.
 
 Specifically, for brown: draw a line  half way between 

Brown      #A52A2A and
FireBrick #B22222

and prerependicular to a line connecting these two colors

  That line separates reds from the browns.
 



 Voronoi Tesselation reference
--------------------------------

A computational geometry algorithm that takes an n-dimensional space
with a given set of points within that space, and partitions that
space into areas or volumes.
http://www.prism.gatech.edu/~gtg874p/Research.htm

The Voronoi diagram has the property that for each site (clicked with
the mouse) every point in the region around that site is closer to
that site than to any of the other sites
http://www.cs.cornell.edu/Info/People/chew/Delaunay.html

Hedgie

Outstanding answer... contains the facts, what they mean, and a touch
of humor.  This answerer understands not only his/her material but can
also well read the "gist" of a question (and answer it).

This page will give you all the information about colour concerning
the measurement and control of coloured surfaces such as plastics,
textiles, surface coatings etc.



http://www.colourware.co.uk/cpfaq.htm

Ken13,

Personally, I would call the RGB color you posted (138,10,34) much
closer to red than to brown. It appears to me as a "wine" color.

Brown (assuming red is involved) is sometimes defined as an orange
with low brightness. In order to make orange in RGB, you mix red and
green. Your color has plenty of red, but, while it has some green, the
green value is minimal and is far outweighed by the blue value,
pushing the color towards purple rather than orange.  Your color would
need to have less blue and quite a bit more green.

Sorry, I know that isn't what you wanted to hear.

Fortunately for you, this does not define brown legally (if there is
any such thing). I suspect that it matters much more whether the
particular judge thinks it's brown.

- Hammer

Hi,

Well, there is no strict definition of what exactly is treated as
"brown" color. That name rather defines a group of similar shades
appearing alike when viewed.

There are standards for colors, of course, but they do not define a
color as "red" or "gray", yet colors are given codes. For example -
every color you buy in store to paint a wall, a car or - a door, in
your case has some universal, well-know code, since it's visualy hard
to tell apart when brown becomes red or orange or yellowish (take for
example a color of wood surfaces). Only the most common coded colors
are given nicknames (like Color of Mahagony, Oak, Cherry, etc).
Depending on usage (computer design, painting, drawing, car industry,
etc) of color and location, code standards may differ. Being a
designer, I keep to Pantone's
(http://www.pantone.com/support/support.asp?idArticle=73&) color table
which has one of the widest code tables for my purposes.


From the point of RGB, the "brown" can be ideally defined as 150, 57,
57 triplet (these are values if you put color=brown on a web page),
but as long as R is the highest, and G is greater or equal to B - the
color is in some shade of yellow, orange or brown. Further, if G is
about the half of R (+/- 20%), B is not more than 20% below G and R
doesn't go above 200 (towards orange), then you can be fairly sure you
are talking of some kind of brownish.

And yes, 138,10,34 triplet is definitelly in the sphere of being
reddish towards lilac, not brownish (although I'm more keen to that
than regular brown).

This is all a very interesting discussion :-).  I am surprised that
there are no "scientific" or absolute measures of color.  Is color a
purely qualitative measure and not a quantitative one?

The thing is that colors are formed out of combination of
electromagnetic waves, emmited or refflected from a certain source.
The color depends on wavelength of those waves. Human eye can register
electromagnetic waves having length between 0.4 (ultra violet) and 0.8
(infra red) microns. Now, the number of colors only depends on how
small steps one can make between these two values on emission source.

There is a basic classification of colors, but even this basic
classification has few models - with three or with four primary
colors, hues, brightnes or saturation (RGB, CMYK, HSV/HSB, HLS). What
everyone will agree is that, in RGB model, we have primary, secondary,
tertiary, etc colors. Primary colors are red, green and blue.
Secondary colors are orange, purple and green, as colors having the
equal amount of primaries, while teriarty are russet, citron and
olive, made up on same principle, etc.

The amounts of R, G and B added in combination can form numberless
shades and common colors. People who deal with colors will usually
form their own or use some already made better-know "palettes" in
which they put their set of colors chosen this way and give them codes
or name them. These palettes will vary in form of labeling colors,
amounts mixed, granularity of shades, etc. This is made different
mostly because of the purpouse where color is applied.

For example - take Web color palette and some facade palette. Web
palette, as computer based, will be formed out of RGB values from 0 to
255, while facade palette can be formed with amounts of RGB in far
more finer steps. Also, there is a difference how colors appear in
different environments - if you make a color on computer mixing 255 of
R, 255 of G and 255 of B - you will get pure white color, while if you
take real colors and put the same amounts of base red, base green and
base blue - you will get ... um, well, some shade of gray. So, if
white on computer is not the same as white on house facade, even
though they are made by combining primary colors on the same
principle, it's hard to expect that computer brown will be exactly the
same as brown applied on wooden door. Thus, different palletes can
hold a same color labeled as "brown", but depending on where the color
is to be applied, the exactly same looking color to the eye may need
to be formed in different ways. This results in that we don't have a
universal formula to make a certain color.

However, going back to the beginning of this comment, after the color
is applied on some surface, we can measure the wavelength of reflected
light from that painted surface and say that some color has a certain
wavelength index and check if a color from one palette matches the
color from another. Brown will have somewhere around 0.6 microns of
wavelength in reflected rays or say it's "an orange of low brightness
and saturation" and that is about all that is certain in deinition of
color spectrum range we call "brown".

You can have alook at image of whole spectrum here
http://skyserver.sdss.org/dr1/en/proj/advanced/color/whatis.asp.

If you are interested in knowing more about colors, you can have a look at 
http://www.efg2.com/Lab/Library/Color/index.html for reference
material (there is a comment there saying: "Brown can only be produced
by a yellow color surrounded by brighter areas. We perceive something
as brown instead of yellow when we think its reflectivity is very
low.")

You can also have a look at these for more info:
http://jeff-lab.queensu.ca/stat/sas/sasman/sashtml/gref/zgscheme.htm
http://www.bozzle.com/pb_Colours.html

Wow.  Thanks for the comment with many good resources to study.  There
appears to be no simple answer, however :-(.

Try this as well : http://desktoppub.about.com/od/colorpalettes/l/blcpbrown.htm

Since you're refernecing your door, a physical object with paint, I'd
say it's RYB. If I'm not mistaken, an equal combination of red,
yellow, and blue creates pure brown. What you'll want is a color with
a pretty equal amount of red, yellow, and blue in it.

Hmmm... OK... I will have to see if I can measure this.  I know that
my door is not "pure" brown... it is cherry in name.  Now, is cherry a
brown color?  Back to the original question this is.  This continues
to be a great discussion :-).

This is one of the more fun discussions!
Lots of great answers above, especially the colourware link.
Essentially, most things to do with colour are subjective, and all
colour using industries use some form of reference colours. You cannot
describe a pantone colour - simply give someone the number to go and
look at it and see if it is the same as a colour they have!
If it came to a dispute in court between you and your neighbours (a
hypothetical situation I assume!), I can guarantee that both sides
would be able to find an resepcted expert witness to swear under oath
that your door was brown and was not brown.
Part of the problem here is that the colour is brown. From a
scientific point of view, you can stick a sample of your door paint in
a spectrum analyser and find out exactly what combination of
wavelenghts of light it is reflecting - its true colour fingerprint if
you like. This does not help tell what colour people see it as though!
Also, the 'pure' colours from a single wavelength of light are the
ones from the rainbow - ROYGBIV, not brown, which has to be a mix)
Taking your side (where a broad definition is required) I would take
the simpler view of a 3 primary colour defnition (Cyan, Magenta,
Yellow for reflected colours) and go for a definition of
CM=Blue/Purple MY=Red CY=Green and CMY=Brown. In other words, anything
with any mix of all three colours is brown!
I susepct most people would subjectively disagree if they looked at
the colours produced where one of the primary colours was very much
smaller, but still it would be difficult to refute that the colour
could NOT be called brown!
I suspect that none of this helps at all, but it is interesting!

The interesting thing about color is that it is highly influenced by
culture as well as the obvious human vision.

http://www.straightdope.com/classics/a2_168b.html

Many cultures don't even have a word for brown, or many other colors
for that matter.  The English language does pretty well, but we still
have issues as well.  After all, in the spectrum, where does red stop
and orange take over?  Is the traffic light yellow or is it amber? 
Teal or Aqua or blue-green?

When we want to quantify things, the easiest way is to go straight to
the emitted wavelength.  For instance, light with a wavelength of
630nm (in a vaccuum, folks), is commonly called red.  You won't find
too many people who'll argue that fact.

Now, as the wavelength changes, it turns into what we call orange,
blue, green, etc.  Just because we don't have a specific name for the
color of 601 nm light and how it differs from 602 nm light is more a
deficiency of the human language than that of scientific applications.

You also have to take into account the sensitivity of the human eye. 
Can one really tell 601 nm apart from 602 nm?  Probably not.

Then, you get the mixed colors, like white.  What happens when you
have light that is a blend of wavelengths?  Well, that's when you get
colors like white, brown, and the like.

There is no unique color, "brown".  Rather, it is a blend of light.  
From art class, we remember that we can mix red and green paint to get
brown.  Try that with light and you're left with yellow.\

I think in a legal aspect, though, it comes down to the board on the
HOA.  Often times, we have to look at the spirit of the law, not the
letter of the law.  By understanding the purpose of the law, it can
clear up a lot of confusion when such questions are posed.  The
purpose of this law is to ensure all doors look alike.  If your door
is obviously different than everybody else's on your block, it won't
matter if your door is brown or cherry or purple.