What a cool concept! I like the idea of mixing colours, and thus needing to selectively apply the different characters' shots, and thus needing to find a way of blocking it.
The isometric movement broke my brain a bit, because you e.g. go left up if you press up. Given that this doesn't appear to be tile-based, it seems unnecessary to make the controls difficult. You mention intending "weird controls" above, so I don't know if this is intentional, but I for one just get frustrated by it; I think the aspect of controlling multiple characters at once is already a challenge, and a thinky kind of one, rather than a frustration one.
Speaking of, I loved the idea of controlling multiple characters, though I would have liked to see some kind of indication as to which one will move according to my input (as opposed to being mirrored to that character); it made confusing controls even more confusing. Also, perhaps an indicator to show where the character's shot will go would be good? Otherwise you're sometimes just taking shots and having to restart if you missed it by a hair.
Overall, clever idea, though the controls made it difficult to enjoy it properly. Still, very creative and cool concept. Well done!