Mr. Laser Beam wrote:
Starfleet Marines exist, and in TOS, they wear black uniforms
In TUC there is a Colonel West, he is a Marine. While he seem to be wearing a Starfleet uniform, the uniform is actually the generic uniform of the "armed forces" and is wore by Starfleet, Marines and if there is such also Army personnel.
It's not solely a Starfleet uniform.