Like a lot of blokes, I'm slightly red-green colourblind.
It hardly manifests itself in everyday life. I find it difficult to see when the amber light has turned to yellow-green on my Apple wifi router. And I'm slower at picking raspberries than other people. I can see the red fruit and the green leaves, but they're tonally similar and obviously shine brighter for others.
And now I can't read the Guardian's football page. The little bars are coded green, red or grey to show each team's run of form. Actually I suspect a lot of people will have trouble picking out these lines.
Designers please note: key distinctions should not be made in small areas of red and green.