Fun little game! I like that you incorporated the tutorial into the game world. Took me a bit to notice that you need energy to switch colours, though, and it must have slipped past my mind while reading the description.
The volume of the music and sound effects should be about the same, currently the music is barely audible when the sound effects are at a comfortable level. Mr. Blob seems to be a cute happy little blob. It felt strange, however, to see he's still dented and not round while jumping. At least he seems to be round in general because he rolls downwards smoothly and has the dent always at the hill's side.