I'm in the samme boat as Peter. Color blind people have trouble with color shades that blend together, such as those green and yellow examples. We need sharp contrasts: Blue, Dark Green, and Yellow (but only with a really dark blackground) are ok. {two points if you caught the pun}
I lose yellow if it is on a white background, the various shades of light green look like yellow to me, dark greens and brown are the same, light blues and violet are the same, and dark blues are the same as purple. I think this is typical for the color challenged.