Simple looks but big brain game!
You made a cute looking Game with OldSchool mechaniks feel new with the Color part. I could think of alot of extentions with this, like cleaning colored trailes with boxes and open paths befor you can color connect crystals. etc. Maybe some other units which take away your space of movement.
Over all its a very nice game, and the theme of spreading your slime over the whole map is also funny!
NIce submission!