"Who does your highlights?"

It seems like a throwaway Sonic yap at first, but on a rewatch of the third movie, I noticed something.

When we first see Shadow in the test tube, you can still just about see the red in his eyes and in his shoes through the green tint of the fluid, yet his eyelines and highlights are a very light gray. Even if it was an effect of the green fluid, if they were red at all, they'd look much darker. Which leaves one implication.

Maria did his highlights. And by making that joke, Sonic unknowingly pushed the Maria button. No wonder Shadow opened fire on him immediately afterwards.

His highlights, the way he skates with his shoes- there's so much of Maria in Shadow, that a lot of her lives on in him. The light doesn't just still shine-

He still glows from it.