Cannot get colors in Paper Buttons Row

Hey there,

for hours I am trying now to get colors to work with Paper Button Rows plugin.
I am using the latest version and installed all available updates.
All I am trying to do is giving the button a default color and a different color if the sensor is active. I am only using the main theme.

I tried to create a minimal example:

type: entities
entities:
  - type: custom:paper-buttons-row
    preset: mushroom
    buttons:
      - entity: sensor.tv_living_room_input
        active: Apple TV
        styles:
          '--pbs-button-rgb-color': red
          '--pbs-button-rgb-active-color': green
        #state_styles:
        #  Apple TV:
        #    button:
        #      color: red

The sensor sensor.tv_living_room_input currently has the value “Apple TV”.
But no matter what the value is, it should be red or green?

But the Button is always gray/white.
I even tried the state styles (see commented part), but without success.

Can anyone see a problem here?
I even tried a different browser, deleting cache and so on.

Thank you so much!