DJI didn't choose red and green. Just go look at any boat, plane, helicopter etc etc..........
But they did choose white, I guess they did that for stealth against a bright sky.
Ever try to find a landed drone on pretty much any ground? White shows up best. So then the next question, why not white on the top and something darker on the bottom? Because when you lose them they often land wrong way up!
But if you asked me for a solution, I'd have it like a search and rescue vehicle, white with orange stripes, easy to see from top and bottom and against light and dark.