OK, pulled a connection appart on a "white" strip ... referring to the four copper connections where you cut the strips, positive is connected to (surprisingly) the positive wire and the other three are joined with a bridge of solder and connected to the negative wire.
Logically to make the primary colours you'd connect positive to positive and then the negative to either R, G or B as required.
On one of my strips RGB isn't marked, but it appears that the standard colour sequence is + G R B
If it's any help the new uprated RF controller is a vast improvement on the IR controller usually supplied with the strips.
Hope that helps.