As for the emissivity of paints perhaps a single layer sheet of the composite
you intend to build your flying machine with can be used for tests. Paint
small
spots with the actual paint you's like to use. Place the sheet out in the sun
and measure the temperature from the reverse side at each spot using your
radiometer. Do this as soon as you place the sheet in the sun.

Sounds like a reasonable test. If I only had the time. Mine will probably be
white.

I used to be a gunsmith, you can keep your Glock™

I intend to. 8 years, about 11 cases of ammo, 2 misfires from bad factory
ammo, and one from the gun due to stupid owner. It hits what it is pointed at,
now if I could just point it better...........Other than that I'm happy with
it.