FR: add icon-on/off theme color

[Mariusthvdb]

for more flexible theming, and making boolean/switch/toggle icons stand out of regular icons, it would be very helpful to have a theme variable for icon-off.

we now have

  paper-item-icon-color: blue                                                      # Icon color
  paper-item-icon-active-color: red.                                          # Icon color active

but the plain icon-color is for all icons.

if one wants to have eg switches use an on and off color, and not use the regular icon-color, this seems not possible.

compare with the toggle

  switch-checked-button-color: blue
  switch-unchecked-button-color: red

which allows us to do that.

would be a real improvement if we could have those for the icon too.

  boolean-on-icon-color: blue
  boolean-off-icon-color: red

or simply the on-icon-color/off-icon-color.

hope you will consider.

it would make custom-ui obsolete, and allow us to set this in core HA, and not have to resort to custom card-mod-theme (which is not very robust) or card_mod (which would be an enormous heap of labor setting on each toggle) for. simple frontend effect.