I believe that in times past, a black flag raised during or before a battle meant "no quarter", i.e., that all of the opposing soldiers were to be killed, not taken captive. Didn't Mexican General Santa Ana raise that "no quarters" black flag before the final assault in the Alamo?
Seem to be remembering, but haven't looked it up.
As to colors, the official color of the state of Connecticut is white, signifying purity. The flag has a blue background. Don't know where black came in. Same for those hideous silver uni's.
Time to get back to the state's colors.