First, you are given a white ball. Roll it into the red ink and then roll it onto the small red target.
I did all the 15 free levels. What I particularly liked was watching the colored path that each ball took. I think Blendamaze would be particularly appealing to kids.
There is a logical puzzle element: when a ball enters a color, it will emerge from one of several holes. But these types of puzzles really amount to trial & error.