I've painted all of the skyights on my last four campers white to match the roof. Clean the sky light, and use Krylon Gloss White spray paint after making sure you tape off the roof. This was the first mod I did to my brand new Montana when I tool delivery. Keeps the heat form getting in the unit. Unlike material between the domes, the heat never gets in. If reflectix is used between them, the heat is still in your roof.
Before
After
And the inside that still lets light in, but no heat!