I could absolutely see a dresscode being enforced heavily if it was seen by the opponent during the match, then a choice of color or style could be done to mess with the opponent, but they sit at a table, the opponent can't see his pants, as long as the pants would be acceptable for an IT guy in an office, they should be acceptable here
Wow I never had a comment about any clothing in my IT jobs and I just wear whatever I would otherwise, almost always jeans in some form for the lower body. Graphic tees, band shirts etc quite often as well. I'd hate to work in a that stuck up environment.