Color Effects is a neat app, for what it is. Being able to selectively saturate /de-saturate an image can make for a unique image, but it’s rather rare that I use it. That said, I like this app for how simple it is. After taking or selecting your image, it shows up black and white. From there you use your finger to paint over the parts you want to return to the original, color version. With the ability to zoom in and change brush size, this is actually a fairly simple way to create the effect–maybe even easier than when do it on my computer.
I wouldn’t pay for this app and it’s certainly not a must-have, but if you want something new this could be a fun way to go.