Real neat game idea!
Reminds me of Ikaruga, where you can absorb matching colored bullets but be hurt by the opposite bullet color, so you have to change between the two colors.
Very clever to have it so that you can only hurt the enemy with the opposite color + having to attack in a different colored side to replenish bullets!
And it seems like there is a rogue-like progression, every time you lose, new rooms and layouts appear.
I can see this being very addicting!
Great work on this game! :D