HI Tg 747-300, Buzz here. I've seen Boeing build it's wheel wells and color them white - so it's easier to find leaks. The DC-8's we had had a primer green color wheel wells and not many lights, so it was always a gloomy place at night.
Primer green would be for accessories inside: spoiler mixers, flap transmissions, torque tubes - which might have an orange/black spiral painted on them. The APU bleed air duct often has a black shroud around it, and is a golden color - titainium plated with gold for skydrol protection.
That amazing AV8 corrosion preventive spray gives a golden brown transparent color, it's made by Dinol. We used to use LPS-3 but that stuff was always slippery / sticky. The Dinol AV8 will dry to a hard film so you don't get so messy as you rub up against it.