On the Declare War screen there are the two check box lists, Enemy Allies and Call Allies. I know what selecting the check boxes do, but what do the two possible colors represent? Sometimes the check boxes have a gold border, sometimes they are silver-blue border.
Declare War Screen, what do the check box border colors represent
europa-universalis-iv
Best Answer
The checkbox indicates if an enemy should be co-belligerent. This means, they should be considered to have a military alliance and able to call their own allies in the war.
The box is grayed out when the co-belligerence is forced. For instance, attacking a vassal will always have their lord enter the war as an ally. Else, if it is not grayed out, you can chose the status yourself.
In general, if you chose not to have an enemy to be co-belligerent, then this enemy will not be able to call in their own allies, and taking provinces from them will cost twice the diplomatic power. The converse applies as well. Exception: In the case of forced co-belligerence, they are not able to call in their own allies.