Headset cable (with 6 cores)
I would say you are correct. If there are 6 cables, (assuming that this is a normal pair of headphones with only a mic and two speakers) then they would probably be 3 ground cables and 3 cables going to each respective part of the headphone. This would mean that there would be a ground cable for the right speaker, the left, and the mic. 

Usually, the darker cable out of the pair is ground. Sometimes this may not be the case. You could also see if there are any stripes or white lines on the cable. If so, then that cable would be the positive line. 
As well, in your case, I would assume that all bare copper cables are ground. To make sure of this, you could always use a multimeter and check the voltages. If you put the red probe to one of the speaker lines and the ground probe to ground you should be able to make out which line is positive just by looking at the polarity on the multimeter. 

One last piece of advice, you should look at some teardown videos of the Razor Kraken. You should hopefully find a video that will tell you which cable is which.