Here is what I used to force any state-icon with binary_sensor to be green when off and red when on:
- type: state-icon
entity: binary_sensor.entry_doors
style:
top: 21%
left: 97%
"--paper-item-icon-color": lightgreen
"--paper-item-icon-active-color": red
Not sure this approach works on temperature though.
Also, what I meant with filter is you can use filter: opacity(n), n=0 (invisible) to 1 to change visibility of images especially ones with state:
- type: image
entity: group.garage_mvmnt
camera_image: camera.carport
filter: opacity(.4)
state_filter:
'on': opacity(1)