I have two pekins, one is 5 yrs old female, the other is about 3 yrs old drake. They are still going through their last molten phase now, put as of today, it has rain, then went into freezing rain and as I type this msg it is snowing. They both are a bright yellow. I just went out to check on them and their yellowish is fading. Yes, it depends on the weather. During the winter, it's to keep them warm, during winter, depending on how cold it is they turn a dark yellow. Food and water have nothing to do with it. It depends on weather.