Hi Leman! The skin colours/rendering looks good to me! What would help with the realism I'd say would be to focus a little on the structure/anatomy and the values that describe it. The head looks small and some other minor things stand out to me like the shape of the nose, flat right shoulder or her left arm that seems a little twisted. Also describing the clothing and the hair might bring it together a little more:) When you are drawing from reference (or otherwise really) try to focus on the 3 dimensional shapes not just the outlines, would be my suggestion. Did a little paint-over just quickly fixing some of the things that stuck out. Hope that helps a little:)