FWIW - From what I've read, Black units, "Immunes", were heavily utilized in combat, during the SAW and Philippine Insurrection campaigns, under the false belief that Black men would be less susceptible to Tropical Diseases than White Troops.

Some of the transport ships, going to Cuba, had 'color lines' painted on the Decks to segregate the Races. This was irksome to some (Regular) White and Black Regiments with a history of serving together on friendly terms.

During WW1, there was an apparent policy to deny Black Units a combat role and the intention to relegate Black Soldiers to transport and support roles.