Why do my hands and lips turn purple when it’s really cold?

18F no diagnoses, not taking anything

This is a pretty recent thing for me; my friend likes to out that my lips are purple and this happens during very cold weather and has been happening since I was 16. Just an hour ago I was freezing cold and noticed that my hands had turned purple/red but they quickly returned to their normal colour once I warmed up. What’s going on ?? My dad’s a community nurse so he has the blood oxygen checker thingy that I always use for fun and my blood oxygen levels have always been normal (98-99%)