Color Check:
Color Check determines the color difference and contrast between any two colors. You can check your own color combination by specifying the hexadecimal values of a foreground and a background color below. You can check if your color combination passes Checkpoint 2.2. For example, color combination of #ffffff and #cccccc does not pass Checkpoint 2.2 for the following reasons:

Brightness:
The difference in brightness between your foreground and background colors is 51 and is therefore insufficient. The W3C recommends a standard of 125 or greater.

Contrast:
The contrast between your foreground and background colors is 153 and is therefore insufficient. The W3C recommends a standard of 500 or greater.

Source: http://www.etre.com/tools/colourcheck/

Colorblind Web Page Filter -- See your web site through colorblind eyes with the colorblind web page filter.

To show obvious differences in colors, please check how our images from "red flowers" category will be viewed by someone with color blindness.

This is how people with normal vision see the page	protanopia (red/green color blindness; no red cones). It is difficult to distinguish colors between red and green with similar intensity (brightness). "dark red" appears almost as "black."
deutanopia (red/green color blindness; no green cones). Difficult to distinguish colors between red and green with similar intensity (brightness).	tritanopia (blue/yellow color blindness; no blue cones). The distinction between blue and green is more difficult.

Source: http://colorfilter.wickline.org/

Color blind image correction

Some good image examples viewed by someone with color blindness.

Source: http://www.vischeck.com/daltonize/

Try Daltonize on Your Image Files
Images can be Daltonized before printing. Print applications where legibility is essential (for example, public safety documents, maps, and technical instructions) can all be made more legible for color-blind users....

http://www.vischeck.com/daltonize/runDaltonize.php

Images that are friendly to color blind people

Set of colors that is unambiguous both to colorblinds and non-colorblinds

	Black (0,0,0)	Avoid the situation where important information is conveyed only in the form of color. Use magenta instead of red. avoid using red characters on black backgrounds, including blackboards For red, vermilion is used since it is recognizable also to protanopes. Colors between yellow and green are all avoided, since they are indistinguishable with yellow and orange. For green, bluish green is chosen so that it won't be confused with red or brown. Since violet is close to blue and appear the same to colorblinds, reddish purple is chosen. Between vermilion and yellow, three colors with different apparent intensity is selected. Sky blue and blue are chosen so that they are distinguishable with there difference in brightness and saturation. Even for non-coloblinds, thin lines and small characters in blue and yellow are hard read. For thin lines and small objects, use darker blue and orange is preferable to sky blue and yellow. When combining colors from this pallet, Use "warm" and "cool" colors alternatively. When using two warm colors or two cool colors, put distinct differences in brightness or saturation. Avoid combination of colors with low saturation or low brightness.
	Orange (230,159,0)
	Sky Blue (86,180,233)
	Bluish Green (0,158,115)
	Yellow (240,228,65)
	Blue (0,114,176)
	Vermilion (213,94,0)
	Reddish Purple(204,121,167)

Source: http://jfly.iam.u-tokyo.ac.jp/html/color_blind/index.html