Quite wonderful.
I wasn't sure what kind of game to be expecting when I started this, and I was pleasantly surprised. I'm actually not sure if I've ever played a top-down shooter where the camera moves around the person like that, so it was an interesting new experience for me.
Anyway, the controls worked well (although I completely forgot about running until after I had beaten the game...), and the three colors were implemented excellently into the game. It very rarely seemed obnoxious, which I was happy about. The enemies had just the right amount of difficulty, and the ability to build up ammo quickly was very satisfying. The ninjas and normal enemies had some AI that was a bit more interesting than just following the character (like when they veer off to the side or run away), which was also nice.
As everyone has said, this would've been even nicer with sound effects and music. And perhaps a better ending. And maybe a story. But now I'm stretching it a bit, and the game would probably become cumbersome and less pick-up-and-play with a story. The boss fight was fun, though it took me a little while to understand how to do it. Do I shoot him? Do I bring him to the electricity and shock him with it? I figured it out eventually, but perhaps if you had put some sort of an indication that he was being protected by the side things, it would've been a bit easier.
...or maybe it's better having to figure it out. I'm not sure...
All in all, this was a fun game to play. I had a good time, and I hope you continue to make games (hopefully with sound).
-Trekopep