how to connect 4 3W RGB in serial together?
The series (not serial) connection would be: 

input voltage, protection resistor, R+, R-, G+, G-, B+, B-

The input voltage should be about the sum of the voltage drop across each diode. Although this may not work well, because each type of LED will have very different characteristics. It's better to connect LEDs in parallel and have each driven by a constant current source.