My butty in college is 17 years old , he has purple fingers , his fingers are slightly smaller then his classmates (but not out of the norm) what I mean it looks like it shrank, I never wanted to approach him about it, can anyone explain me why ? (one more thing I don't know if it helps you, but I'll say it anyway in the winter he tends to get cold wile other classmates aren't cold)

It sounds like your friend has some circulation problems?

When blood is oxygenated in your lungs it turns bright red. As it moves throughout the body giving up oxygen it eventually turns to a darker red/purple color. If your friend isn't moving enough oxygen those areas tend to become purple/bluish in color. How are his lips?

It is possible your friend is anemic. Are they vegetarian?

It sounds like your friend has some circulation problems?

When blood is oxygenated in your lungs it turns bright red. As it moves throughout the body giving up oxygen it eventually turns to a darker red/purple color. If your friend isn't moving enough oxygen those areas tend to become purple/bluish in color. How are his lips?

It is possible your friend is anemic. Are they vegetarian?

No he is not a vegetarian, and only his fingers look funny there purple, skinny shrunken fingers

Some vegetarians are iron deficient, and iron is one of the components of blood so that was my reasoning on that.

Without knowing more, it's difficult to say. It is your call on whether to ask him about it. He may be self conscious.

Hope it helped.

It could be raynaud's disease, which I happen to have.

Raynaud's is an extreme reaction to cold
Raynaud's Disease (http://www.mayoclinic.com/health/raynauds-disease/DS00433)

The fact that his fingers look "shrunken" is likely just your perception. Maybe he just happens to have smaller hands.

I don't suggest asking him about it. He's old enough to have done research or have spoken to his doctor if he's concerned. Its possible he already knows and wouldn't want it brought up. People comment on my purple hands all the time - it gets annoying. ;)