Idea: Alternative use for notes:
Those notes you pick up could be used to "infuse" a white block with that notes power.
So lets say you have a white block on the blue line, then you "infuse" it with "Purple power", then suddenly that note sends out 3 blue balls, instead of 1, it basically acts as if you have BOTH a Blue & Purple note on that column, but it's just from 1 block there.