Crayolas, M&Ms, ugly fabric, and commercial color challenge are all ones I have participated in.
The commercial color challenge was a little different. The coordinator had a bag full of things we got to pick from. The things were napkins, greeting cards, food labels, book covers, etc. We had to make something using the same colors in the same proportions as our thing.
The crayolas we drew two and had to use those colors. The M&Ms we drew one and could use the complementary color straight across on the color wheel and either black or white.
Ugly fabric, you put a fat quarter in a paper bag and pass them out. We had to use at least 50% of the ugly fabric and not just for the binding.