Board Thread:Theories and Speculation/@comment-1512913-20161125200227/@comment-734582-20161127095011

I agree that the Rinnegan and Sharingan are different eyes. But i also think the Rinnegan is not directly part of the Sharingan line but rather a mutation. That is, it combines powers over reality (e.g. what a "red rinnegan" like we saw Momo use would have) with power over death (signified by the purple color). Similarly, it seems that the Tenseigan is a combination of Byakugan + power over nature (senjutsu).

This may seem weird, but i think what happened is that whereas all these powers were united in Kaguya, Hagoromo and Hamura each got roughly half their power. So, whereas Kaguya had general powers, in Hagoromo and Hamura they were able to specialize in their Dojutsu.

As to obtaining the Rinnegan, it's clearly a Kekkei Genkai. Merely getting Hagoromo's chakra isn't enough, you need the Kekkei Genkai. After all, Obito's eye would've turned to a rinnegan when he obtained Madara's rinnegan, and Kakashi should've awakened the rinnegan when Obito gave him Six Paths chakra. Furthermore, Sasuke should've gotten twin rinnegan if that was all it took.

Therefore, it's clear that Hagoromo's chakra (six paths chakra) but also the Rinnegan KKG are needed to awaken that eye. And it seems that only Indra and Ashura possess that Kekkei Genkai.