Blue Sky is a free iOS app coming out of China, where skies are often gray and air pollution is often out of control. Of course, China isn't alone with that problem. Blue Sky is sponsored by the World Wildlife Federation and an advertising agency, Ogilvy and Mather, based in New York and Shanghai.
Since it's Earth Day, I thought it might be appropriate to point out this little app. It's simple in concept and execution -- you take a photo or select one from your camera roll. With your finger, paint in a bluer sky on the photo you've loaded. It's easier if you have a pretty flat horizon. The app doesn't let you magnify your photo to work in tight places, and there is one and only one brush size.