The first is comfort. Due to the sometimes extreme cold, practicality is foremost, staying warm.
Ties are the usual attire for administration personnel.
As the Band Director, it is much simpler. Basic black is best, whether it is a black turtle-neck or black or very dark shirts and pants. The reason is simply visual, or the lack of it. The musicians must be able to see the baton and hands for instruction. Black, or very dark, background allows more visual perception of the non-verbal instruction.