Mr Dixon's job application was turned down by Strathclyde Police on the grounds that his colour blindness raised concerns about health and safety and reliability of his evidence. However, an employment tribunal rejected his disability discrimination claim on the grounds that it was submitted more than three months after the alleged act of discrimination.

Mr Dixon later found out that colour blindness is a much more common condition in men than women. A tribunal has now allowed his subsequent claim for indirect sex discrimination to proceed even though it was brought outside the normal time limit, using its discretion to consider claims brought out of time where it is "just and equitable to do so".

It's worth noting that it is unlikely that the most common form of colour blindness, inability to distinguish between red and green, would come within the Disability Discrimination Act 1995. To be covered, there has to be a physical or mental impairment that has a substantial and long-term adverse effect on the person's ability to carry out normal day-to-day activities.

The guidance on matters to be taken into account in determining questions relating to the definition of disability (PDF format, 125K) (on the Equality and Human Rights Commission website) says that it would not be reasonable to regard "simple inability to distinguish between red and green, which is not accompanied by any other effect such as blurring of vision" as having a substantial adverse effect. This is by far the most common form of colour blindness. However, the guidance goes on to state that it would be reasonable to consider "inability to distinguish any colours at all" (a very rare form of colour blindness) as having a substantial adverse effect.

It will be interesting to see what the employment tribunal has to say about the sex discrimination claim. The case is expected to be heard later in 2008, in a joint claim with another colour-blind applicant rejected by Strathclyde Police.

The New Scientist website has an explanation of why colour blindness is more common in men than women.