I know there is a blue topaz, but blue diamond, I am not so sure of.
Yes, there are blue diamonds, the most famous being perhaps the Hope diamond: http://www.si.edu/Encyclopedia_Si/nmnh/hope.htm

Bee-YOO-ti-ful bike!!!!!

And you've given me an idea as to what to do with the diamond wedding band I no longer need; congratulations on your new bike, and thank you!