Comb turning dark red/purple

[Username382]

My roosters comb turned dark red/ purple. What do I do, and what can cause it?

 

[Eggcessive]

Welcome to BYC. When the whole comb turns dark or cyanosis, that means he is not getting enough oxygen to his heart for whatever reason. It is not a good sign. Is he stressed in any way? Could he be dehydrated? Are there other roosters who may have kept him from water? How old is he?