Pros 
- Nice meditative game for relaxation and development of concentration
- Lots of categories to choose from
- Hundreds of engaging pictures for free
- No in-app purchases
- New pictures appear every day
- You needn’t buy paper or pencils to start coloring
Cons 
- You cannot add the colors you want
- Contains commercials
- If you spend much time coloring pictures, it may negatively affect your vision