Generally speaking, black tie for openings, or white tie if you have it and it’s a big city and you’re cool with being one of only a handful. For regular shows in the US, I think you can wear pretty much anything, though most men will be wearing a suit or at least a sport coat. If chinos and a blazer is what you have, you will be fine, which is to say that you will be a bit under-dressed, but you will not be the most under-dressed there. If you own a dark suit, I would wear that instead.
