Sith Pureblood? Is that why Anakin grew those orange eyes?

Honestly I have wondered that myself since it seems to be a common trait among the sith. Sith was originally a race of aliens that was nearly 100% force sensitive and aligned with the dark side. Dark jedi humans discovered them and interbred and I guess adopted parts of their culture and created the sith religion. So to distinguish religion from race, they are called "red sith" or sith purebloods. Even though they are far from pureblood anymore lol By Anakins time, I think they are basically extinct.