Given the locations of most of the mega-churches in the Houston area, I'd be amazed if they weren't primarily white. OTOH, I've also seen billboards advertising black-oriented non-affiliated churches, some of which might qualify as mega-churches.

Side issue: does it frost you as much as it does me to see churches ADVERTISING ON FUCKING BILLBOARDS all over town? Those things don't come cheap, y'know; one wonders how many poor people could be fed with the money these places are spending on promotion.

I'm tempted to start a grassroots campaign: every couple of months, send one of these churches a single sheet of paper with the following message on it in the largest font that will fit:

STOP PAYING FOR BILLBOARDS. DO JESUS' BIDDING - FEED THE HUNGRY!