It’s late and I’m tired, so I’ll just offer this for commentary.
It’s fine to wear dark jeans with a navy blazer. Just remember that the informality of jeans provides a lot the of contrast. Pair this with a white spread collar and navy tie and it looks kind of like you were trying for a suit but wore jeans because that’s what the cool kids do. Keep the elements casual and the navy jeans on navy jacket plays much better.