Lights Group entity button not changing colour

I am wanting to create a button in one of my views that will turn on/off a certain group of lights. At the moment my lovelace code is:

title: Main
icon: mdi:sofa
  - type: entity-button
    entity: group.living_room_lights
    name: All Lights
    icon: mdi:floor-lamp

An entity button appears in the view as expected and clicking on it will turn on the group of lights as expected however the button doesn’t show the current state of the group. All it will show is the blue floor lamp icon, it never turns yellow (assuming I’m using the default ui colour scheme). Anyone know how to fix this?