I found this color tool for webmasters to help pick complementary colors in designs. But the coolest thing to me is that it lets you see colors from various types of color blindness (Wikipedia). In the bottom right you can select the type of vision you want to filter by, and it has eight different types. My Dad is color blind. I don’t know what type he has, but its interesting to see that some of the diseases cause people to see almost no difference between otherwise disparate colors.
For example, with Protanopy (1% of men have it) there is very little difference between orange (60 degrees on the color wheel) and green (180 on the wheel). Yet there is a large difference between the two shades of green immediately next to it. Strange. This image shows the colors as normal people see them on the left and the protanopy colors on the right. If you look long enough, you can see that the bottom right is slightly darker than the top right.
