[infogulch]

The entire underside of these satellites is a big phased array antenna. Maybe you can paint it so it absorbs all the other wavelengths, but it would be counterproductive to absorb the radio wavelengths used by the antenna itself since ground emitters would have to increase the gain to get through it.

[DoctorOetker]

communication link bandwidths are typically miniscule compared to optical spectrum of the sun

[infogulch]

Sure, maybe you can find a paint that is black in all bands except for the ones used by the satellite. It won't use carbon black.