This is a great challenge, but a little hard to describe without sounding confusing...
Using a stamped image (can be stamped or digi) color only 2 parts of the image using two different colors. You can use any method you can think of to add color (marker, pen, paper piecing, etc.).
Thankfully, Hannah's card beautifully depicts what we're looking for:
On the elephant's cheeks you'll see some pink, and the baby's blanket is blue. The color is understated, and yet the image stands out perfectly!
Don't get me wrong, I'm a sucker for lots of colors, patterns, etc. on an image, but sometimes a little bit goes a long way. And that is what we want to see on your cards.
It can be challenging, as Hannah discovered, trying to decided which two parts should get the color, but once you settle on them you might find that all the image needed was just a little touch of color.