I have 3 RGB things connected to my iHost Zigbee.
I don’t think any of three are made by Sonoff. With the RGB bulb I can choose colour and brightness in the scene. With the 2 RGB LED I can only set them On/Off, although Node Red lets me choose colour/intensity with same device and iHost. Haven’t tested it to see if it works though. I am certain I can adjust the colour and brightness manually though.
My suggestion is to homogenise the scene interface for RGB devices as I didn’t realise scenes could select colour till this evening.