Colour Picker and Tester

Can your audience read your web pages? About 8% of men and a few women are colour blind.
To use this tester, click on the radio buttons.

 
Background
 
Text
 
Difference in brightness:
 
Contrast:
 
Difference in total RGB value:
 
    Colour-blind visitors:
    Please give me feedback on how well this works. I would like to know:
  • Are the colour models for your type of vision accurate?
  • Are any of the three measures of difference in brightness indicators of how well you can read the results?
 
This sample text is designed to show what a block of text looks like in your chosen colour, on your chosen background. It is presented without adjustment, for monitors with THOUSANDS OR MILLIONS OF COLOURS. It should change colour as you click the buttons on the left.
 
This sample text is designed to show what a block of text looks like in your chosen colour, on your chosen background. The colours have been adjusted to simulate presentation on monitors with 256 COLOURS. It should change colour as you click the buttons on the left.
 
This sample text is designed to show what a block of text looks like in your chosen colour, on your chosen background, to a COLOUR BLIND READER (PROTANOPIA). It should change colour as you click the buttons on the left.
 
This sample text is designed to show what a block of text looks like in your chosen colour, on your chosen background, to a COLOUR BLIND READER (DEUTANOPIA). It should change colour as you click the buttons on the left.
 
This sample text is designed to show what a block of text looks like in your chosen colour, on your chosen background, to a COLOUR BLIND READER (TRITANOPIA). It should change colour as you click the buttons on the left.
 
Browser note: On a Mac, this page works in Opera 5+, MSIE 4+ and Netscape 6.0 (if a little flakily) but not Netscape 4.7. Any other browser feedback gratefully received.
 
Since publishing this page, many people have contacted me with useful colour-blindness resources. Here are two of the best: Technical info, image demonstrations and Photoshop CLUTs to download and See how your webpage looks to a colour blind person.