I'm 30. The part of nail plate above lunula in both thumbs looks a bit purple-ish. Dont smoke, no fungus. Could feeling cold cause this? What is cause?

See MD. You need a full history and clinical exam. The differential diagnosis can be from simple vasospasm from being cold, to cyanosis, to other problems. If you are short of breath with exertion I would seek care immediately in the ER. Otherwise if you feel fine see MD.