So I have a headcanon that SATAM Tails was actually born gold in coloration and his eyes are blue. Before they were separated, his mother dyed his fur a brownish orange to hide his golden color.
This is because it is believed that foxes born gold with two Tails are actually the infamous ninetails who feeds on the souls of others for power and to extend their lifespan. Bloodlines which carry this trait are considered to be cursed and are not accepted by fox kind.
After 10 years, the brown dye finally wears off and his true golden color shows through. As for how his eyes appeared to be black, it's actually just an illusion which is a side effect of the dye. In really bright lighting, the blue in his eye does show through, but since no one ever looks deep into his eyes long enough, they never notice.

Poor Tails had heard horror stories about the ninetails and how terrible they are. Once he discovers that he's one of them, it causes him great distress and makes him question himself and if he could truly be a freedom fighter. Poor kid.

I'm honestly surprised with how well this turned out since this is the first time I had drawn SATAM Tails since I was a child.
This is also the first time I had been able to draw with smooth THIN lines. I used to only use thicker line because I thought I could never draw smooth thin linework.