I don’t change my bags to match my shoes.
I don’t change them to match my outfit or weather.
I even rarely change them to match the occasion… unless it’s a very special one.

What I do match them to is the size of the book I need to carry.

… which really only matters enough to mention because my shoulders and neck are a mess, and I always wish I could carry a smaller and lighter bag, 
but can’t actually make myself carry a smaller book.