“Why will we use green lasers for starwisp and light sail propulsion?
“Because stars aren’t green. Can’t be green, in fact, because a black-body spectrum that peaks in the green is broad enough that there’s plenty of other-colored light to make it not sum to green. That makes green the least stealthy color in space.
“So when you’re going to be shining a few hundred terawatts into someone else’s star system, a monochromatic 530 nm green is as good as it gets in letting them know up front that you aren’t trying to sneak something in on them.”
– Argil Medanis-ith-Medanis, Laserider Network