Look at the trio. All of them have a snow-y palette, which all in all, looks pretty strange. Xerneas face and it's horns are almost the same too.
Is it possible their shiny colors might still change? Like GameFreak didn't plan to release the Shiny Trio anytime soon, so they scrapped coloring them correctly. I know it never happened, but they just look weird.
Yveltal is badass with that white line and grey scarf though.