I have never seen the word Yuan Ying in Taoist scriptures. It should come from a novel, corresponding to Yang Shen.
There is no mention of color in the Taoist scriptures, only that it is invisible. Neidan can become a Yang God when he grows up. Moreover, this Yang God went to the moon step by step, and he was not afraid of fire and water. When he gathered together, he became angry.
In addition, Buddhist practitioners have heard that the color of Yang Shen is milky white, and the purest is milky white.
Some people are milky white with gray, while others are milky white with pink, depending on the level of practice.
As for us ordinary people, we are basically black and red. Mixed with killing, lust, hatred, etc.