During winter, when the birds are less fertile, and when birds are normally moulting, the combs do lose colour. This has *nothing* to do with diet.
If birds have worms so badly that their combs lose colour, the birds are severely anaemic. This would be an extreme situation.
It's *normal* for birds to lose wattle and comb colour in the "off" months. When the birds are ready for breeding, the wattles and combs become bright red and more plump. This is a hormone at work and is designed to signal to a rooster that the females are ready for breeding.
It's a very good thing at the very end of winter to worm your birds in preparation for spring and the onslaught of eggs. Nobody wants to have an egg withdrawal period due to worm medicine right after they begin to lay again...
Linz
