Heyo!! Sonic fanart!! Yayy!! TONS of my headcannons in their designs!

Shadow's inhibitor rings are more similar to silvers but with chaos energy within them.
Shadow's sclera is tinted yellow due to his black arms genes.

Sonic's quills have patches of Gold due to how many times he's gone super! As well as the tips of his quills being lighter, They'd grayed thanks to the stress of the Metal Virus.
Sonic is FtM!! Lightning bolt top scars!! Rahghagahghgh

And that's about it!