If the host enables observers, players can get assigned the wrong color (i.e. red instead of blue), the wrong player number (i.e. player 2 instead of player 6) and their race can get changed (i.e. random instead of human).
How to reproduce: Host a map that has more than 1 force/team and enable observers. In the lobby, have at least 1 player join each force/team. Then have another player join the observer team and then switch back to one of the non-observer teams. When the player does that, WC3 will give them the wrong color. If it doesn’t give them a wrong color, it may change their race. This is not just a visual issue in the lobby, it has the corresponding impact once the game starts. You can have multiple players with the same color.