I'm only 19 and i often find my feet and legs turning purple/bluish when i stand or even sit. what can i do to prevent worse issues in the future?

Vascular issue: This appears to be an issue with your blood vessels. There is a condition called raynaud's phenomenon which often manifests with purplish, painful toes and fingers in response to cold stimuli. This could also be a localized blood clot. Speak to your primary physician who may order tests or send you to a specialist. In the meantime stop smoking if you smoke and keep toes/fingers warm.

See a doctor: You need an evaluation to find the cause of the problem and prevent future trouble.