For example:

<ItemAttribute backgroundColor="0, 0, 200" textColor= "255, 255, 255" criteria="w">
        (itmGetProperty gSource 'foo)

        (cat "Foo: " (itmGetProperty gSource 'foo))

If this functionality were added, the existing labels (damaged, military, radius, etc.) could be defined using it, so they could be changed by mods. And other similarly flexible labels could be added.

See also:
Military and Illegal tags should be unique colors