Dark side of the Bubbles

Just a little test i did to see if i could creat some coloured bubbles, i couldn’t find the proper way to colour them with compositing nodes, so I had to do it in post pro.Anyway, here it is:
http://2.bp.blogspot.com/-m2R-nXQf718/TeB6rzRtmtI/AAAAAAAAAMw/5YOsnhbeBDg/s400/darkbuble.png