I liked it; the color mechanic was interesting. Good for your first game, definitely!
What I thought about the mechanics:
The jumping was a bit floaty. On one level, I had to jump on top of a slime that was moving down a slope of platforms, but I kept missing because I misjudged how fast/slow I would fall down. Personally I'd prefer if the character fell a bit faster. I noted also that there were som tight spaces that the character looked like he could fit into but couldn't, so some minor refinement of the collision detection might be in order.
Only being able to touch things of your own color is a pretty neat idea for a puzzle platformer. You could definitely make something more of this. Spend some time refining the puzzle design - a lot of the puzzles in the game were really simple or required you to do precision jumping around color orbs or just ignore them altogether (which isn't bad - games are supposed to start off easy after all). Maybe explore other ways to control the color of the character? Like, change color with a button press, or levels where you change color automatically every few seconds or where the color orbs are moving or being shot out of a cannon... Or have the colored areas change their color or position. Think moving color elevators? There's a lot of exploring you can do with the mechanic, I think.
Graphics weren't the most appealing, but then again I didn't get the feeling that this was a big deal to you when making the game. My advice regarding the graphics is that the character looks a little out of place in the environment. It might help if the rest of the game looked a bit stick-figurey, or like something that someone doodled in a notebook, just like the character. I don't really have a lot to say about music, but I thought it was ok.
Overall, I liked it. If you want to do something more with it, yeah, go for it. Then again, you probably have other game ideas you want to try out, and in that case it might be better not to spend too much time refining this one game when you can learn so much more by trying a lot of new stuff.