I think you are worrying about nothing.
He looks very healthy.
The colour of the combs changes colour easily. It can change because of health, but also just due to temperatures and even the birds mood. My roosters can have dark blue and purple parts if they are upset, also bright cherry red, darker red, and pale areas.
The yellow poop just sound like the nasty smelly ones they have sometimes.
If the bird is acting normally and is eating, drinking etc, and not acting sick, I would not worry.
He looks very healthy.
The colour of the combs changes colour easily. It can change because of health, but also just due to temperatures and even the birds mood. My roosters can have dark blue and purple parts if they are upset, also bright cherry red, darker red, and pale areas.
The yellow poop just sound like the nasty smelly ones they have sometimes.
If the bird is acting normally and is eating, drinking etc, and not acting sick, I would not worry.