Skin colour change... down there.

This might sound like a weird question so please reserve judgement lol 😅 I’m in my late teens, and I’ve always had very fair skin and my labia majora (aka my lips) has pretty much always been the same skin tone as the rest of my body. Now I’ve noticed it’s gotten darker. I shave often but always have... Is this normal? Or perhaps something to do with the dry air or just growing older? Anyways, just wanted to know if I should be concerned or if this is common lol. Thanku for any input 🙏♥️