This is the kind of challenge that makes you realize how often you rely on a rainbow of colors in card making.
So here it is: Use an image (stamped or digi) on your card and only use 3 colors (and not different shades of those colors). Black and white are the exceptions to this rule. Check out Kim's example:
How cute is that Digi Doodle image? And a fabulous card it is, Kim!
It looks like her three colors are brown, red, and peach (or something close to it). I think it's pretty straightforward, so let's see what you come up with...