1. Go to bottom tool bar and click tribe.
2. Click diplomacy in the overlay (shaking hands tab).
3. If you have the correct rights it will allow you to set tribes as
allies,
NAP's or
enemies.
4. What ever you have chosen will now be coloured on the map for all your tribe to see. Note it doesn't colour the other tribes map, they have to set the same diplo.
Hope this helps