From The Battle for Wesnoth Wiki
The [label] tag
The following keys and tags are recognized in [label] tag:
- text: Visible text in label.
- team_name: Name of the team that can see the label. Label is visible to everyone if this is empty.
- colour: colour of the label. Format is r,g,b where r, g and b are number between 0 and 255.
- x: Location for the label
- y: Location for the label