How can I highlight a certain author in a Category Archive page loop?

I'm building a custom theme. On the category archive page, I want it so that in the loop the posts written by a specific author show up first and in a particular format. For example, I want posts by author with an ID of 3 to show up at the top of the loop and have a blue border. Then, I'd like posts by all other authors to show up afterwards with no border.