Place the print code after you have set the values so for example you could put it at the end of the void RGBCommonLED::updateLED(){ definition.
OR
If you want to be able to print from anywhere then move the definition of the rgb[] array so that it is global. That is move it to outside a function to the start of the sketch. Then you can put the print statements anywhere you like,
P.S. Forgot to include a semicolon at the end of all the print lines, now corrected.