I don't know about you, but I used to love coloring as a kid. I could color in the lines at a young age, so I would exercise this ability whenever possible. Coming across this app, and realizing its potential, was a revelation. Color Fashion by Reallusion — for iPhone, iPad and iPod Touch running iOS 3.0 or later — is a pretty cool little app. If you like playing with color masks for your pics, you'll enjoy this.
When I initially downloaded this app, I was unimpressed and pretty determined to give it a poor rating, but after playing with it a bit, it won me over. The purpose of the app is to allow drastic tinting in your pictures through use of masking. You color in the masked area with your finger, using a small variety of brush sizes and hardness. Then, you use a lasso-type tool that finds the edges of the area. Then, select your shade of tint, and don't forget to make it drastic.
My only complaint with the app is the interaction when painting the mask in. It's frustrating because the gestures are a bit temperamental. If you work at it, however, you can succeed at making some wildly tinted pictures that look really sharp. It's just a matter of getting used to the touch interface for something as detailed as editing photos. If they had a larger selection of brush sizes and hardness, I think it might be a bit easier, but that's just me. I tend to be a bit of a perfectionist when it comes to these things.
If you take a lot of pictures, and want to make some of them a bit more creative looking, you might give this a try. The $0.99 price point is not too steep for what this app offers in functionality. I think you'll like it.