Hyperpigmentation around lower lip line and upper lip:

The visible half of my upper lip minus the central triangular (?) part is a darker shade (almost purple) and the lower lip line is brown, unlike the lower lip itself which is bright pink or pale pink (it depends).

I have no idea how. As a kid, I was careless and never used sunscreen or lip balm. Thanks to that, I have a farmer's tan (HELP) which really stands out as my forearms, even after lightening significantly, have a yellowish tint unlike the rest of my body (which is more neutral).

I would expect sun exposure to lead to evenly pigmented lips, but I look like an alien instead. It really stands out when I'm not directly facing a light source. I assume this might be genetics but those with lip hyperpigmentation around me usually have more evenly darkened lips