Now retired kayaker but for decades I painted my expensive kayak paddles basically as BigHorn described.
I used a combo of the most brightest most reflective colors I could find, usually the orange or yellow or green colors in combination. Usually I painted the back side of the blades not the powerface.
The purpose was to make the blades easier to spot should I loose the paddle but primarily to make my paddles unique to spot and less attractive to potential theft.