A dark comb and wattles can be caused by several things: hot or cold weather, poor circulation (heart problems), or trouble breathing (respiratory problems/respiratory disease). What are his other symptoms, if any?
If he's acting relatively normal, it may be just because its hot outside. However, if he's acting lethargic, it could be heart problems, which can't really be treated. Finally, if he's having trouble breathing/sneezing/coughing, etc., it could be a respiratory disease.