http://www.xrite.com/custom_page.aspx?pageid=77&lang=en#!

This is a really great test for all you designers out there.    

FACT: 1 out of 255 women and 1 out of 12 men have some form of colour vision deficiency. Take the online colour challenge, based on the Farnsworth Munsell 100 Hue Test.    

Apparently

I scored 4 which I think is OK, good enough to make me safe when at traffic lights at least.

Have a go