I might be getting here a bit late, but the reason that the SR71 was
painted black (and called the Black Bird) was because it needed to
radiate the maximum it could on the ground to get rid of the heat of
flying at Mach 3+.

The plane would actually glow red at altitude.

BTW - according to my sources, and now that the sucker is retired (even
though many things about it are still classified), they did try
different paint schemes, and black was the one that allowed them to get
rid of heat the fastest!

Later,
Steve.T
PP ASEL/Instrument