The Color Palette Challenge I use is the one by FallenZephyr that I found on DeviantArt. But any kind of palettes' collection would work. It's more about using colours and colour combinations that you would not think of on your own.
Here are few of the first ones I did:
(you can almost feel the struggle coming off of them)
Here are some of the new ones:
All the Color Palette Challenges I did are posted and tagged on my tumblr blog here.
A.

