I give this game a 7 because I think it has a very strong base and very good gameplay. However, I feel that the controls need some major work. There should always be an option of using either the WASD or Arrow keys for moving, period. This gives your players more choices and lets them use whatever they feel comfortable with (you might prefer WASD but no everyone does, myself included).
I like how each different color has a special ability, but why is the S key used for the yellow ability and the space bar used for the other two? It would seem much simpler to just use space bar for al three. Often I found myself pushing space accidentally to get the yellow ability, then dying. Also, can there be a key that changes to the next color instead of a separate key for each color? I had to "train" my fingers to memorize which color goes with which key, which was slightly frustrating.
I do like the different colored platforms and having to sometimes change colors in mid-jump to make it. One glitch I found was on the first boss level (level 10?). After dying once (not the first time though), there was a boos in teh first black pool and one in the second black pool. The one in the first pool never moved (which makes me think it was a glitch) but he could still kill me if I touched him.
Overall, a good game. Just needs some control tweaking.