The military has white chem-lights, but I've never needed them. All things being unequal, you will get the "best" light from a blue or green chem-light.
You will get the most useful/longest lasting but dimmer light from red.

It all depends on what you're trying to do.
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Member of the toughest, meanest, deadliest, most unrelenting -- and ablest -- form of life in this section of space, a critter that can be killed but can't be tamed. --Robert A. Heinlein