Colour Blindness and webdesign

Approximately one in twelve people may not be able to use your web site properly due to some form of color blindness. At best, your site won’t look to a color blind person as you designed it, at worst, this could mean that text is unreadable, navigation unusable and elements are invisible.

Most color blind people can’t distinguish between shades of red and green. Shades of these colors appear lighter to color blind people. The most common forms of color blindness are:

• Protanopia ­ unable to receive red, andDeuteranopia ­ unable to receive green

A much more rare form is found in:

• Tritanopia - unable to receive blue

How can these problems be counteracted?

• Don’t use color as the only visual clue
• Always underline links
• Provide other means to distinguish between sections
• Avoid using only red and green in your design
• Maintain a high contrast between text and background
• Always put "alt" text on graphics