Mega Charizard Y is likely to have the same shiny colours as normal Charizard because they are pretty much the same apart from of course, their stats. But Mega Charizard X is completely different. Sprites haven't been announced for shiny Megas yet though. The best thing to do is to get a shiny Charmander, and find out!!! :)
Hope I helped!!! :D
EDIT: here is what I think is actually looks like... ![enter image description here](/pokebase/qa-plugin/https-img-proxy/image.php?key=1438e75c78ff148e&url=http%3A%2F%2Foi39.tinypic.com%2F2w69zxf.jpg)
So yeah, he is teal with orange highlights and red wings.