Three toned fingers

My friend’s fingers have a dark tinge where it’s close to the nails on both hands. It’s about a cm wide and then the skin lightens drastically and then to her original skin tone so it looks like she’s been wearing weird gloves in the sun. *She’s 24 *Asian - Chinese heritage *having this for years, but it has gotten worse recently. *No pain but occasional numbness so maybe it’s something to do with circulation? *otherwise healthy though sometimes tired from long working hours, poor sleep.