A free program for Android, by Color Apps For Free.

You are an artist! A true artist never stops working, no matter how old he is. That’s why, in this free coloring game, you will be able to create beautiful pixel artworks, such as a dragon or a unicorn, or even a landscape or a city. Your only job is to fill the blocks with a color, and it’s up to you which color you will use. 

But that’s not all! You can create your own pixel artworks in any size, from a small pixel art to a huge pixel art.