Change
Light entities are now required to set the supported_color_modes and color_mode properties, and a warning will be logged asking users to report an issue if that's not done.
In addition, a warning will be logged if the light reports an invalid combination of supported_color_modes or a color_mode other than ColorMode.UNKNOWN, which is not included in the light's supported_color_modes.
In the Home Assistant 2025.3 release, the warnings will be removed, and lights that have still not been upgraded to a color mode or that violate the color mode rules will no longer work.
More details can be found in the documentation.