I like how you used the theme, it leads to pretty interesting gameplay.
However, I find it a bit of a letdown that what stops you from playing is running out of lives, not mixing the blue character.
I think it would lead to more fun gameplay if instead of only increasing the number of red enemies, you also increase the blues. (or if you did that, but I just didn't get that far, then do it earlier.)
It's a pretty fun game, and audiovisual quality is neat.