My artwork for Mega Charizard X, one of the Mega Evolutions for Charizard in Pokémon X and Y. The shiny colors are based off photos of peoples' screens so they may not be 100% accurate. Many shiny X/Y Pokémon are known at this point, so when I get the time I plan on going back and adding shiny versions of my artwork to the appropriate files.
Edit: Changed the shiny version to be slightly brighter and fixed the colors of spots I missed before. Again, with only photos of screens to go off of, it'll be hard to know for sure if the colors are 100% accurate.