The capitilization of the B is an artifact of the util.KeyValuesToTable. The keys all become lowercase when imported anyways.
The problem is that you are using the default scoreboard (as jam suggested) which only makes 3 distinctions (admin, player, and connecting). Anyone with admin access (superadmin, admin, or anything inheriting from them if you've defined custom groups) is colored green. People connecting are I think yellow, and everyone else is blue. It doesn't check teams at all, just access and connection status.
If you want it to use the team colors you will need to use a custom scoreboard that is designed to do so (ie. sui_scoreboard).