I have had several rooster have this happen with their combs, and I haven't lost one,yet.
I went out to feed one morning and two of my roosters had purplish ends on their combs. I went out a couple of hours later to be sure everyone had water and both of their combs were red again.
I have found no rhyme or reason for this to happen, and they have been different breeds, and ages.
A few years ago, I was worried because I was told that it was probably lack of oxygen due to heart failure. My rooster is still alive and kicking, so unless he is exhibiting any other signs or symptoms, I wouldn't worry about it.
Hope this eases your concerns.
Angie