At risk SC - 1.4.3 Contrast (Minimum)

Based on some discussions with Bruce and Phill Jenkins, some food for
thought for our discussion of at risk SC today....

The attached file uses a set of colors that according to the Brewer palette
[1], when used in combinations to differentiate areas on a map, are color
blind friendly. I was surprised at some that pass and some that fail:

(See attached file: Contrast Comparisons.html)

Some "in the wild" examples of colors that fail that were surprising:

http://www.w3.org/WAI/GL/
White text on dark orange at the top is 3.86 - would only pass for large
text

http://www.nfb.org/nfb/Default.asp
White text on purple background is 4.7 - would only pass for large text
Yellow text on purple backgroud is 4.37 - ditto
(Interesting that the color contrast analyzer doesn't provide any test
results for the text on the orange background?)

http://www.yahoo.com/
Yahoo! Home tab - White text on dark background is 3.58
Orange text on light background is 3.81

Also, I'm curious why our equation for contast ratio is lighter color over
darker color. Isn't light text on a dark background easier to read than
dark text on a light background? Isn't it also affected by the percentage
of the area in each color; i.e. 50/50 of the light color vs. the dark color
is better than 90 light/10 dark?

[1] http://www.personal.psu.edu/cab38/ColorBrewer/ColorBrewer.html


Andi