RGB color lamps have two different controlling system.
1. With its own remote.
Manufacturer installs a signal receiver inside of lamp when producing, and then use a remote to send signal to the lamp, it changes color once it receives signa order. But there are some factors influence the lamp can't receive signal from remote.
a. Customer stands too far from the lamp.
b. Customer doesn't point the remote directly to the lamp, he mights point to other direction, sometimes, it is not very good as TV at home as the lamp is installed underwater.
So, customers will complaint about it, they want 100% synchronous.
2. No remote, but controlled by external RGB controller.
A complete fixture=RGB Lamp+Transformer+ RGB External Controller
Mostly all lamps needs DC12V or DC24V Input Voltage instead of AC12V or AC24V, because the controller requires DC, so people needs to buy a transformer in AC85-265V input, but DC12V or DC24V for lamps.
but how to choose a transformer?
for example, if you have 5 piece 9W RGB lamps.
if you want one lamp with one transformer, so you need to buy 5 piece transformer, which each one must be higher than 9W.
if you want one transformer for 5 piece lamps, so 5*9=45W, you need to buy one transformer more than 45W.
2). RGB Controller
itis the same calculation way as transformer.