Colors you can differentiate from one another by type (power vs hand vs misc) and see from a distance so they hard to misplace. I use dewalt for powertools, kobalt for hand tools, and bright, but different colors for everything else e.g. pony clamps, neon craftsman levels. This makes it easy to put everything away, and spot when you are looking for them in the middle of working and you don’t know where you put something. Several thumbs up for a random, but interesting question!