Custom UI change color of icon

Configuration
4

It’s not correct, but it lead me to find what worked.

Don’t ask me why but it has to be …state == “1” or with three equal signs.
I also believe you made a typo with return return rgb on state off?

The working code in configurator.yaml is

switch.sonoff_1000000000:
  friendly_name: Kaffekokaren
  templates:
    icon: mdi:coffee-maker
    icon_color: if (state === 'off') return '';  # this returns the icon in an unchanged state
                if (entities['counter.counter'].state == "0") return 'rgb(255, 0, 0)';
                if (entities['counter.counter'].state == "1") return 'rgb(235, 20, 0)';
                if (entities['counter.counter'].state == "2") return 'rgb(200, 50, 0)';
                if (entities['counter.counter'].state == "3") return 'rgb(150, 100, 0)';
                if (entities['counter.counter'].state == "4") return 'rgb(100, 150, 0)';

Now I just have to fine tune the color changes.