Hi there , skin tone or color usually is primarily due to the presence of melanin
in the skin. Skin color ranges from almost black to white with a pinkish tinge due to blood vessels underneath. genes are usually responsible for the variation in skin color.
The natural skin color can be darkened as a result of tanning
due to exposure to UV light. day variation is usually due to dryness and hydration but not actually in tone , avoiding direct exposure to sun and using sun protections will help.