Board Thread:Theories and Speculation/@comment-26889573-20151008053113/@comment-1872728-20151015164039

The way I think is that the Rinne-Sharingan is the result of mixing special Nature Energy (Shinju), and special Physical/Spiritual Energy (Kaguya). So the Rinne-Sharingan is essentially the result of mixing Senjutsu with Dojutsu (Byakugan). Hamura would then inherit Kaguya's original trait (Byakugan), hence no Senjutsu abilities. Whereas Hagoromo will inherit that mutation, hence the brown hair instead of the normal white hair. Hagoromo has the Rinnegan, and the Rinnegan mark on his forehead, indicates that this mutation had once again split into two: Senjutsu and Dojutsu. Then Asura would later inherit that mark, which is the Sage Mode Hashirama has (scroll up for explanation), and Indra would later inherit that eye, which is Sharingan.