Entity conditions

I am monitoring an APC SmartUPS 750 and want to change color for an entity depending on a condition.
Right now I have …

  - entity: sensor.ups_status_data
    name: Status Data
      style: |
        :host {
          color: red;

but I want color ‘red’ only when the entity’s value differs from ‘OL’
I have tried but don’t get it right … how can it be done?