I'm not sure what color scheme you'd like to go with, but as a colorblind user, the green and yellow colors that you're currently using are very similar to me.

Perhaps you could do a colorblind mode that uses red, blue, and yellow (out of simplicity's sake) to indicate availability? It'd make your service way more useful for me :)

It's too sharp on a black background with black text. On a high-end display it's just too.. rich a colour. I'd use pastels personally.

Look for a palette you like here:

http://www.colourlovers.com/