I would disagree, wearing brown has several advantages; if you have to change a tire after you get back from your 12 day trip, oil stains blend right in on brown slacks.
When the hotel comes to pick you up they can more easily identify you on the curb because of your "brownness".
No one will confuse you with "real" airline pilots. (All "real" airline pilots wear blue, right??).
You won't confuse your uniform slacks with your interview suit.
Lastly and most important. You match the uniform of your local UPS delivery guy (except for the shorts )