No, the only requirement is height. There is a specific measurment but I don't recall it. If the white light is above everything else on the boat, and it meets Coast Guard visibility requirements, you'll be OK.
2015 Seaark 1872 MV CC Etec-90
Two Helix 12 CHIRP SI's, , MinnKota Riptide ST80/i-pilot Link, Bob's Hydraulic
Bitter Gun Owner