Sensor that works with state_color on dashboard

I have an energy monitoring smart plug that I use to monitor a device, but not to turn that device on and off (currently, at least). To tell whether the device is actually on (it has it’s own switch), I monitor the power usage using the smart plug, and have added a sensor in config.xaml as follows:

sensor:
  - platform: template
    sensors:
      guest_room_bedside_light_on:
        value_template: >
          {% if ((states('sensor.guest_room_bedside_light_power') | float) > 0.0) %}
              on
          {% else %}
              off
          {% endif %}

When used on a dashboard using the following definition, I see the on and off status, but the state_color is not having any effect. What more do I need to do to get state_color to react to the on/off status?

type: vertical-stack
cards:
  - type: entity
    name: Guest room bedside lamp
    icon: mdi:desk-lamp
    state_color: true
    entity: sensor.guest_room_bedside_light_on
  - show_name: true
    show_icon: true
    type: button
    tap_action:
      action: call-service
      service: script.toggle_guest_room_bedside_lamp
      target: {}
    name: Toggle Guest room bedside lamp
    icon: mdi:desk-lamp
    entity: sensor.guest_room_bedside_light_on

Found the answer - simply change sensor: to binary_sensor: