What Causes The Skin Of Entire Body To Turn Bluish/purple Suddenly?

OK,
Let me start off by saying that I have somewhat pale skin, but it's not all that pale when my skin is normal you can't see my veins at all. But often times my entire body will turn Quite bluish/purple, for no apparent reason. It has been doing this for as long as I can remember, and I have no Idea why this happens.
What could this possibly be?

Thanks