I haven’t had this issue specifically but I’ve noticed when adding color changing bulbs, the color changing ability doesn’t show up in Home Assistant until I change the color in the dashboard of zigbee2mqtt. After that, home assistant recognizes the bulb’s capabilities. What hub do you have?
Problems with Zigbee2mqtt
I run HA in Docker and I have set up Mosquito MQTT and Zigbee2mqtt in other containers....