All the Blueberry ive had was always bright green. I dont think they call it Blueberry because of the color... more so the taste and smell. I could be wrong though. Like Vancefish said, cooler temps near harvest time will bring the colors out in alot of purple strains.
Check out The Attitude seed bank for pics of different strains... see if they have one the color you like. The advice about losing the intake fans and making them all exhaust is very wise. It works much better that way.