Outdoor activities make our skin tan. The only option is to wear protective full sleeves clothing and cover as much as possible. Usage of a cap or hat and umbrella is encouraged. Skin already tanned can be treated with de-pigmenting creams and other oral medications. A good skin care regimen comprises 4 steps - cleansing, toning, moisturizing and sun block. Based on your skin type, a dermatologist will recommend you appropriate products.
Use a lipbalm with sun protection.
Avoid self medications. Certain medical causes of darkening of lips should be ruled out.