Not really. Upn has a lot of black actors. As well as Wb.
This is done to gain momentum in the Urban market, because it is deemed hip and is a growing demographic. There fore they develop a fan base. Once they have built a base, they usually dump those "urban shows". Like Fox did, "True Colors", "Living Color", South Central". And what UPN and CW (WB) are doing. You know, 7th Heaven, Smallville, Supernatural, Gilmore Girls, Reba.
WET, doesn't need to be stated, as it is NBC, CBS, ABC.