Red skin for men and yellow skin for woman is a convention of tomb paintings. Those are the stylized paintings on walls with the stereotypical technique of comb

Red skin for men and yellow skin for woman is a convention of tomb paintings. Those are the stylized paintings on walls with the stereotypical technique of combining a side view and a frontal view into a single 2D representation. Mummy portraits belong to a different, later genre that is far less stylized and more realistic. The skin tones, in particular, are more true to life in mummy portraits than tomb paintings.