I saw this on a web page about a year or two ago, forgot to bookmark
it, and am kicking myself for it because I can't find it anywhere. 
There was a company or artist - European or possibly Scandanavian -
who had created a set of mugs in a gradient of colors corresponding to
the color of coffee or tea with varying levels of milk or cream added.

They would send you a color chip, and you would make a cup of coffee
or tea the way you like it.  You would then match it to the
appropriate chip, and then buy a set of mugs that correspond to the
color.  That way, anyone mixing your coffee or tea in the future could
just make it look like the mug.  Can someone help me find this product
please?

Hi mopower,
 
I beleive you are referring to British designer ONKAR SINGH KULAR, who
has created mugs to match the exact shade of a person's preferred
milk-to-tea ratio. Onkar Singh Kular used the Pantone range of colours
to create 128 mugs which colour gradually changes from beige to brown.
 
 
Onkar Singh Kular website:
http://www.kularsoflondon.com/
 
Design Museum - Onkar Singh Kular
http://www.designmuseum.org/design/index.php?id=74
 
 
"You can order the mugs from him directly by sending him the Pantone
chip number you'd like.
Alternatively, you can order a Pantone color chart from his website
(kularsoflondon.com) and hang it on the wall, then everyone can choose
their own color and write their names on it."
http://www.papaya-palace.com/katlog/archives/001058.html
 
 
Hope this helps!
 
 
 
Search terms used:
 
mugs color shade tea coffee designer
://www.google.com/search?hl=en&lr=&ie=ISO-8859-1&safe=off&c2coff=1&q=mugs+color+shade+tea+coffee+designer
  
"Onkar Singh Kular"
://www.google.com/search?q="Onkar+Singh+Kular+"

Sweet.  And I thought *I* knew how to google.