Do OK-to-wake lights actually help with sleep training?

Parents in r/beyondthebump, r/BabyBumps and r/toddlers report meaningful success once toddlers are old enough (roughly 2+) to understand the color cue. Reviewers note it's not magic on night one, but pairing a consistent color change with a clear rule ("stay in bed until it turns green/yellow") is widely described as a game-changer.