Command: team.Setup(ID,Name,Color(R,G,B,A))
Example: team.SetUp(1,'Red',Color(255,0,0,255))
Basically, that would make the team color red. Now for the scoreboard, you would just set the color in from team.GetColor(TEAM_ID)
May I ask what deathmatch gamemode, the only deathmatch gamemode on garry's mod that I know of, is my gamemode?