Use card-mod to add a css style to your group entity
- entity: group.lights_inside
name: Inside
style: |
:host {
--paper-item-icon-color:
{% if states('group.lights_inside') == 'on' %}
var(--paper-item-icon-active-color)
{% endif %};
}
tap_action:
action: toggle
Group is in a glance card. This style will change the group icon color just like a switch icon.