When creating a web form don’t write, ‘the fields with a red dot next to them are compulsory, those with a green dot are optional.’ This statement will be of no use to people who are colour blind, or those using grey-scale monitors, or those using screen readers.
Requiring users to differentiate between colours to access important information can lead to problems. An example would be a navigation button that has red text on a green background, as people who have difficulty differentiating between red and green (the most common kind of colour blindness) will have a hard time trying to navigate the site.
The main colour combinations to avoid for people who are colour blind:
Red/green combinations (memory aid: red berries against green leaves on a tree)
Blue yellow combinations (memory aid: yellow daffodils against a blue sky)
‘The Institute for Dynamic Educational Advancement (IDEA) and Brandeis University’ provide some useful information about colour blindness.