You shadow with a dark colour Eyeshadow/Rouge (for example 566) the sides of the fingers; stay away from the knuckles.
Lighten the top of the fingers and the knuckles with a light colour Eyeshadow/Rouge (for example 001). Continue lightening between the dark lines in the direction of the wrist. The shading and lightening must blend into the basic colour in a natural way. The more subtle you work, the more natural the result.