|I asked around, and the general consensus is you CAN paint the shower area. There are several products you could use. Rust-oleum has a kit to paint your tub / tile but it only comes in three colors, white - almond and biscuit. I'm sure if you searched around you could find some other companies with more vibrant colors.
As far as the glass goes...
There is a risk that moisture would get behind the glass and fog it up. especially if it is an outside wall and it is cold outside. There could be a temperature difference from one side of the glass to the other and you could get a fog on the other side. No one seems to agree or disagree whether it would be OK or not. You would need to seal it all the way around.
How are you planning to fasten it to the wall? With the sealant?
Does sound like an interesting project though and I would be curious to hear how it turns out!!