Well, you have Altaria which looks nothing like a Dragon. Flygon and Vibrava don't look like Dragons either. Then you have Pokemon like Gyarados and Charizard that look like Dragons but aren't. You have a few other Pokemon that don't really look like their types.
Color wise it matches the old Dragon type button. Gamefreak and Pokemon.com still use the Blue/Redish pinkish purple for Dragons.