Does your shell have lights built into it (ie: is it a full shell, including a top, or is it just side pieces)? You can consider adding some color from your
box boom positions, but I wouldn't touch anything from your
catwalk. Remember that the most important thing in a band concert is that the musicians MUST see their music. With choirs, generally it is only the accompanist and
conductor/choir director who need to see music - the singers are usually memorized. With a band, they will all have music stands in front of them, and will need to see their scores. That said, if your shell doesn't have any top light built into it, make sure that you leave enough light for them to see. Use any color that you may add from your box booms as fill (to give it some "mood") but don't use it as a key. The last thing you would need is for the Band Director to yell at you that he needs more light during a rehearsal, or worse, at a concert. Another tip - set levels during a rehearsal that the band is present at. Make sure that, with whatever you choose to do, every musician can see the
conductor and his or her score. This includes the Upstage Sections that are the furthest from any form of light. I hope this helps a little
bit - obviously I don't know your space or the concert material to suggest colors or anything - but hopefully this aids you a
bit.