I assume that you have a suit as well. The suit would then cover the really formal occasions. For example: a date at a fancy restaurant. I think though you need to consider the environment. If you are wearing a blazer and everyone is in polos and tees, that is one thing, another is that is if other people are wearing suits or blazers as well.

That is, if you want a blazer to throw on when you meet with a boss or a customer that might be wearing a suit, you want something more formal on the blazer spectrum.

Put me down for recommending wool navy or dark blue hopsack as well.