T-ara themselves probably couldn't influence this at all, nor do I think anyone would've thought about the colours of their uniform somehow matching the colours from the player uniforms of another team. This is probably a management problem, though of course as I am not an insider I can not judge about this.
People always need to blame someone, of course T-ara being the front-end they are blamed first. (Think about it. If your internet or TV or whatever stops working, you call the helpdesk, if they can't do anything about it directly they get blamed for the stuff not working anymore even though they have no influence on it whatsoever... they are just the ones people have contact with).
As for FC Seoul, I think they handled it nicely saying that T-ara is not to blame for their defeat. Because for the fans they were an easy target after that blunder.
I'm sure that in a couple of months people have forgotten about it and they've learned from this error