Is colorsplash a new app? I didn’t used it before. Beside to make black and white effect, I think almost every app can fulfill that demand. However I am trying to build a good skill in the photoshop. Is this app simple for those purposes?
No. You'll want to try either Photogene, Photoforge or any of the other apps other members have suggested if you want to do real photo editing. Colorsplash gives you only one editing option: cutout. It basically just converts your photo to b/w and allows you to add color back to parts to highlight certain details of the photo such as this:
It's a one trick pony though; you can't crop, resize or do anything else to the photo except cutout or selective colorization.