I like the idea of different colored balloons to keep track of who's talking when, but dark text on a fairly dark background is hard for me to read (not enough visual contrast). You might try dropping the saturation so they're more faded ... closest word I can think of is "pastels" but that's not quite it.It is a great idea though, especially when they're all talking at once. :)
@Sierra: Thanks for your input! On future pages, I'll try some lighter shades while keeping the black font, or adjust the entire bubbles' levels!
Let that thought out here: