There is a lot of very useful research published on the web in this area.  Most of the resources listed here have been developed overseas.  You will notice, therefore, some variations in the spelling of the word 'colour'.  American spelling has been retained in titles and direct quotations from American-based resources.

There are countless resources available on accessible web design.  There are probably others not listed that are just as good, perhaps better.  Those listed below are fairly representative of what is available.

When you look at resources on accessible web design, always check for references to the Web Accessibility Initiative (WAI) guidelines.

Note: In the final resource, links will open in a new window.

Safe Web Colours for Colour-deficient vision

BTexact Technologies

http://more.btexact.com/people/rigdence/colours/index.html

This site contains information on colour blindness as well as tools for design.

The Eye of the Beholder - Designing for Colour-Blind Users

Christine Rigden, British Telecommunications Engineering Journal, Vol 17 Jan 1999

http://more.btexact.com/people/rigdence/colours/colours.pdf

Colour is increasingly used these days to help convey information.  According to this article, one in twelve men has some measurable degree of colour vision deficiency.  The use of certain colours in certain ways can cause difficulty when navigating web pages or software, and even total illegibility in some cases.

This article offers a method for representing images as perceived with a colour deficiency, so designers can produce interfaces which avoid causing problems for their users. 

Some aspects of this article will present some access barriers, due to its layout and use of images to show examples of colour perception.

Seeing Red

IA Think

http://www.iathink.com/2004/01/seeing_red.html

This is an article on the use of red to convey information on the web.

Website Tips - Colour

http://www.websitetips.com/color/

This site provides links to many resources on colour and design.

Colour Blindness

http://trace.wisc.edu/world/web/index.html

Scroll down to the heading, Colour Blindness.  This site gives a list of links to many useful resources.

What do colour-blind people see?

http://www.tsi.enst.fr/%7ebrettel/colourblindness.html

This site gives very useful simulation and checking tools.

Colour Blind Awareness and Support Group Australia

http://members.optusnet.com.au/~doverton/index.html

The author describes the experience of colour blind or colour deficient vision.

Considering the Color Blind

http://webtechniques.com/archives/2000/08/newman/

An easy to read description of colour blindness and some strategies for considering web site visitors who have colour deficient vision.

Colorblind Design Evaluation

http://newmanservices.com/colorblind/default.asp

This online tool gives you three ways to see how colours used in HTML code look to people who are colour-blind.

Colorfield Insight Plug-in (Mac)

http://www.colorfield.com/insight/

You can download a free tool (Mac only) from this site, to test how images would look to people with colour deficient vision.  There is also a tutorial on colour deficient vision.

Vischeck

http://www.vischeck.com/

Vischeck is a free tool for simulating how an image would look to a person with colour vision deficiency.  The examples link gives very useful examples of two different forms of colour deficiency and how they would each affect how a person sees an image.

The site also offers a tool called Daltonize, which claims to enhance images to make colour more available to people with colour deficient vision.

Colormatters – The Future of Color on the World Wide Web

http://www.colormatters.com/comput.html

This site looks at a wide range of issues about the use of colour, including:

• What is gamma?

• Is your computer colour blind?

• How to improve your computer colors

• Tips for Windows from a Pro

• Web-safe colors

• The future of colour on the web

Colors for the Color Blind

http://www.toledo-bend.com/colorblind/index.html

According to this site, it is about:

… color blindness or, more correctly, color deficiency. Briefly, it describes the condition, causes, and effects. The primary purpose, however, is to furnish a set of color charts to aid the color blind in working with computer colors, most especially on the internet and in web sites. There is also some really nice software (shareware/freeware) here for checking colors onscreen on your computer - great for anyone, but especially for the colorblind!

Color Blind Home page

http://colorvisiontesting.com/

This site gives comprehensive information on colour-blindness, causes and effects.  It also presents a simple online test for colour blindness.