My first Reactor 3 was rather green. I called CMG, sent it in, and they sent me another that is much whiter.
Interestingly, they now claim to have changed the packaging so that it no longer gives the impression that your light will be pure white.
CMG has great customer service, so give them a call.
Also, and you can search CPF for this thread, you can put a tailcap from the 2AA Reactor onto the 3AA Reactor. This cap has no resistor in it, and boosts the light quite a bit...making it brighter and whiter.
It also voids any warranty you might have, I imagine...and I haven't seen anyone post here on what this does to battery or LED life.
T.