RE: Equation for determining color "closeness"

I agree with Wendy's point that brightness needs to be factored in.
Arie Arditi says that people with low vision often have color deficits
across all three dimensions of color (brightness, hue, and saturation).


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-----Original Message-----
From: Wendy A Chisholm [] 
Sent: Tuesday, September 02, 2003 7:47 pm
To: Roberto Ellero;
Subject: Re: Equation for determining color "closeness"

Thanks, Roberto.

>I noticed that the complementary colour (directly opposite to each 
>other in the colour wheel) combination has the highest contrast. 

In my experience, red and green are considered complementary [1,2,3,4].
the resource that you cite red and green don't appear to be 
complementary.  Another source names the complementary pairs as [6]:
and magenta, blue and amber, and blue-green and red.

If red and green are complementary, there is at least one exception to
complementary rule: don't use green and red together (unless it is ok to

miss the information presented in an overlap of the two colors).

What about the other definitions of complementary colors? Is it ok to 
overlap red and blue-green? Reading Aries's pamphlet [5] it seems that
on blue-green is OK as long as you use dark red against light blue-green

and don't use light red on dark blue-green.  Joe's book seems to support

this when he says, "Don't set green on red or red on green....unless:
items have considerable difference in brightness....If the lightness 
contrast is _indisputably_ high, you've solved the problem." [7]

So, it seems to me that the "complements rule," while short and sweet, 
doesn't quite stand on its own.  Brightness needs to be part of the



wendy a chisholm
world wide web consortium
web accessibility initiative

Received on Wednesday, 3 September 2003 09:09:41 UTC