h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

Why do people's faces go read when they hold their breath?

I know normally it's because the blood is moving to the surface of the skin, but I don't understand why it is in this case.

For that matter, why does it happen when people are embarrassed?

I'd guess with breath-holding, there's generally contraction of the chest and maybe other muscles, possibly resulting in blood not draining away from surface blood vessels the way it normally would.
If someone simply doesn't breathe, rather than actively fighting the impulse to breathe, they face may not go red as much, if at all.

Thanks, Potholer. I must have missed your responce, !

Well, if they don´t breathe for long enough it starts going a blueish/purplish colour instead. My mom attended a man who choked on his own vomit and his face became swollen and coloured purple like a plum.

Did he survive?

There's a red-haired character, Bradley, in Eastenders who goes red whenever he's on camera, and when he gets into an argument he looks like his cheeks have been slapped. Goodness knows what he'd look like if his face ever did get slapped.

No, he died.

Not a nice way to go, but then, is any?

Not really, My mom says she saw his bloated face every time she went to sleep for weeks afterwards.