Any recommendation for a RGB light Bulb?
Lifx…
Sengled Element Color Plus - great Zigbee bulbs without a built-in Zigbee repeater. These are great when directly paired with the ST hub. Since these are zigbee ‘end devices’, there is no chance of them screwing up your zigbee mesh network if someone physically powers them off.
My recommendation is don’t do it! 
Buy an inexpensive Zigbee outlet and plug it in nearby. You’ll be much happier in the long run. IKEA Tradfri, Security Peanut, Samsung Outlet, etc…