I think the shapes/ faces would be a great addition. I'm sure you're not the only one who will have trouble with the colours. Did think of this pretty early on but lost track and forgot to do anything about it.
^^
That would be really helpful. I get a lot of Color based Puzzle games from my Humble Bundle, I actively avoid claiming them because of my color blindness.. xD
I had a fun idea for a game mode.
Could you make the Balloons come down like Space Invaders and you fire the balloons up at each balloon like a missile command and each one you miss or don't pop one speeds up the decent? ^^
You could even do a Asteroids game mode where a couple of big balloons float across the screen and each time you hit one and bursts in to smaller balloons of multiple colors. :3