Col, I'm sure you're correct, in that UPS doesn't care, but India's right too: brown is an ugly, depressing color to be surrounded by all the time. UPS may be huge, and successful, and a great company to work for, but they look dull, drab, and cheerless.
Color is a mood influencer, and before you start scoffing, think about how soothing colors are used in hospital rooms, bright colors for toddlers, somber colors for funerals, etc. - it does have an effect on people, whether they're concious of it or not. I know I wouldn't enjoy being surrounded by brown, most of the time.
As for the Expedite division, I understand that the plan is to add trucks and vans when and where the business demands - John posted a need for a cargo van in or near Cinncinnatti, not too long ago.