Color thing on the MQTT inbuilt broker

The documentation of the MQTT broker got me struggling for a while with my magicHome led controller for a while:

My working code is as follows

Thing topic ledStrip1 "Led strip 1"
           Type colorRGB : lampcolor "ledstrip1 thing" [ stateTopic="stat/LedStrip1/Color", commandTopic="cmnd/LedStrip1/Color" ]`  

and in my items file I have:
Color Livingroom_Light_ElefantCabinet "Elefant cabinet" (Group_Livingroom_Lights) { channel="mqtt:topic:MqttBroker:ledStrip1:lampcolor"}

In the manual it shown that there is a parameter called rgb=true to the thing configuration, what does this mean? What other optional parameters can you define? It seems to be a brightness value when you send ON command to it, but how to configure this with textual configuration?

I also so several topics on the forum where people not getting that you need to choose either colorRGB or colorHSB in the thing configuration, my problem was that I thought my ledstrip was HSB while it was actually RGB.