Colours in the "Kingmaker" mode of "Stronghold 2" indicate the alliance affiliation of a player or AI. Changing a player's colour changes which other players or AI are friendly or hostile towards him. The player's colour must be set at the beginning of the Kingmaker game. Players do not need to be evenly divided between alliances, and you can select any desired alliance colour during set-up.
Click "The Path of War" in the main menu.
Choose "Kingmaker." The Kingmaker settings screen appears.
Select the icon with four coloured shields.
Click your name in the player list.
Click the alliance colour in the square in the upper-right corner. The colour behind your name changes to match the selected colour.
Change the other settings for the Kingmaker match as desired (no other options in the settings screen can change the player alliance colour).
Click the arrow icon in the bottom-right corner to start the match.