If i knew that a complement was going to be thrown back at me with a 'oh no, i look horrible today' etc, i wouldn't have said anything. IMO it's the best way to go.
Yeah, it's also worth noting this:
If you totally disagree with the one who gave you the compliment, you actually insult his/her own taste.
"You look beautiful in those clothes!"
"Oh no, they're awful!"