Question on cats ears getting red and hot after play?

I have noticed on and off that my orange tabby's ears are red and when I touch them they are warm. I've noticed after play recently they became red and warm.  His is orange, and his ears are very visibly red.  Though after the activity they seem to go back to normal color.  I've noticed when he gets scared or stressed they get red and warm.  They never used to, but he is 9 years old and he's not a kitten any more. Is this something to be concerned about? Or is it normal that when they get older it happens.  I have two that are about a year and a half older than he is and they run around and get active and their ears don't get warm or red.  I do have a 16 year old cat who's ears are kind of the same way. but usually her's are red when she's sitting but when playing her ears don't get red though. Her's just get red when she's stressed.  My concern is maybe high blood pressure?  He's eating fine, drinking fine. He seems normal in every other way accept for his ears.get red when running around and playing. And also when he's stressed out or scared.


Thanks!

It's probably just from his heart rate being elevated and his body temp rising a bit from the exertion of playing.
 

I am in new territory with older cats, so I don't really know about what to expect. My first cat crossed the rainbow bridge at 8,  One at 2 years and another at 8 years. So as they get older, little things concern me  My last one passed of a stroke, so red ears make me think high blood pressure and want to make sure that he's not in any danger  He seems fine other wise.  I plan on monitoring for a bit.