State_color for non on/off values?

I have an entity card with possible values of idle, heating, cooling. Enabling state_color: true has no effect since, I presume, that only works with on or off type values. Maybe others but certainly not the values I have.

What is the best way to get the entity to color when it’s anything but idle? I can think of some round about ways to do it with templates / entity filters or maybe customizations but hoping I’m missing a simpler solution.

Look up card-mod.