Is white a color?  I live in a townhouse with strict rules...I would
like to paint my door white and it may be an issue...however, if it's
not a color, how can they object?

The dictionary defines white as something free from color.  White has
no hue or saturation, which are defining attributes of color, further
reinforcing the fact.  (Color needs to be defined in terms of
brightness, hue, and saturation.)

You can find the definition of white and of color at www.m-w.com

Unless you're painting with light, or RGB :) then white is fully all
colors :). See: 000000 is black and FFFFFF is white.

You can't get legal advice here anyway. (see italicized below). But
White isn't a color in paint any more than (what's the current color
of the door? brown?).

When the restrictive covenants say "color", they mean "pigment" or
something along those lines.  While we can't give true legal advice,
if it were to resort to civil court, the burden would likely fall on
the question of whether a "normal person could reasonably interpret
the word 'color' in the covenants to exclude white."  Likely the court
would frown on that and say that a normal person would understand any
shade of pigment you can pick up from a paint store is considered a
"color".

As it is, there are like 18 shades of "white" at a paint store.  Are
any of them truly void of any color?

http://en.wikipedia.org/wiki/White

White is a color (more accurately it contains all the colors of the
spectrum and is sometimes described as an achromatic color - black is
the absence of color) that has high brightness but zero hue. The
impression of white light can be created by mixing (via a process
called "additive mixing") appropriate intensities of the primary color
spectrum: red, green and blue, but it must be noted that the
illumination provided by this technique has significant differences
from that produced by incandescence.

They can object if they mean they don't want you to use paint sold
under the label "white," regardless of the spectral analysis.

Just speaking practically, I would think the easiest course would be
to ask the ruling body of your association whether you can paint your
door white.  You might also look around and see if any other doors are
white.

If dead flat pure white is not acceptable, any shade even just
slightly off white would certainly have color in it and would probably
be white enough to please you.

Archae0pteryx