For exactly this reason, I applied four colours of fluorescent tape to the sides & front & rear of my drone.
For evening & night flying, I added small red and green LEDs on each side (same as all ships and planes), to be able to determine the direction at a distance. (Port is Red, Starboard is Green. ) It has a white headlight, and I fitted a blue LED taillight.
Very easy to drill a 5mm hole to fit them. I recommend "strawhat" LEDs for wide angle visibility.
Every drone should have them.