It's not working exactly the way I'd hoped, but the idea is that each color of ball corresponds to one of the potential boyfriends!
So if you get all the red balls, you'd get the full set of sporty boyfriend, for example.
Now one issue is that the wet boyfriends colors don't always seem to line up. This was one of the last features to be added, so it is a bit dysfunctional. The others should work well, though! I'm glad you had fun <3