Weird, that's not how they are supposed to be.
- First, check that you are indeed in TDM. When you hold down Tab, you must see two lists of players (one for each team). If there is only one vertical list, you are not in Teams mode.
- If you really are in teams mode, then this is a bug. Try enabling colorblind mode in Options, this should at least change the team colors to black and white.
As it seems to me, though, you are probably in FFA mode and haven't chosen Teams for some reason.
Let me know if this helps please!