Locking teams&colour but allow race selection

[Kacpa2]

Hi, as in title, i wonder how i could lock the teams with set colours but allow them to choose race, i seen that on few maps, i set player's races to 'selectable' but in game it's locked random. Can someone tell me if i'm missing something obvious? I looked for threads like this but i only seen stuff about locking them entirely as i did.