I’ve also now discovered a way to do this:
- Install Hue Advanced (Connect) Hue Advanced (Connect)
This adds the “Reachable” device status/variable - If Device Reachable = True Then Set Colour Temp to Something you like
Whenever the dumb switch is switched off - this is where the above comes in. When the dumb switch is on the default philips hue light colour will change to whatever you set after a second when the hub sees the device has just become reachable. 