I came across these color blends in a post on the web today (to save blushes, I'm not linking) from a mapping developer. Here's what they look like to the majority of us
and here's how 6% of the male population see it (via the excellent color oracle freeware)
clearly the bottom two blends will be very difficult for color blind users to interpret.
Color blindness is a lot more complex than I've explained here but generally blends from yellow to blue are much better than reds to greens. More info on color blindness in maps here.
If you're interested in the more general uses of color in maps, the Haklay text book has a good couple of chapters.