See the lip darkening(melanochelia) happens because of unknown reasons(idiopathic) or due to Vit
B12 deficiency,
ferritin deficiency or cosmetics. And Its tough to get original rosy lips. You can use Sebamed lip balm every 2 hours. Use glomax lip balm morning and night for lightening.
Next Steps
get blood tests of Serum Vit B 12 levels Serum
ferritin levels.