Here is a good primary on accessiblity and colors from a US Government site: US Web Design Systems - Using Color
- Coblis — Color Blindness Simulator
- Color Oracle: Free color blindness simulator for Windows, Mac and Linux
- Colour Contras Analyser: Determine legibility of text and contrast of visual elements.
ColorSafe: Get suggestions for similar colors with sufficient contrast
WebAim Contrast Checker: Web based contrast checker
- WebAim Link Contrast Checker: Checks for link color against body and background
- WebAxe Color Contrast List: List of several color contrast tools