It might be much lower; the OP references “casualties,” not KIA. According to Wikipedia, “A total of 708 African Americans were killed in combat during World War II.” The cited source is not online, however: Micheal Clodfelter. Warfare and Armed Conflicts- A Statistical Reference to Casualty and Other Figures, 1500–2000. 2nd Ed. 2002 p. 584 ISBN 0-7864-1204-6.

Given that the rate of wounded to killed is typically 3:1, that death toll may be about right. Hard to say without knowing about other non-combat fatalities, though.