White is not a color for dragon*con. Black is a far better choice. A black shirt soaked through with sweat doesn't turn transparent, and the dirt, grime, and grease of equipment never shows up against it. There's an art to staying clean, dry, and daisy-fresh at 'con when you're a tech staffer.
I haven't mastered it yet, but part of it appears to hinge on changing shirts a lot.