Odd. Seems that you need to use background instead now for this card.
Ill look into it because --shape-color still works for the Template card for example.
EDIT: --shape-color still works. The light needs to be on for it to take effect. If you want to change the color whether light is off or on use background instead. The remaining syntax is the same. Ill update the guide to make this clear and check whether this also applies to things like the cover card.