Telling Left from Right on unlabeled RCA cables

Get the Sterophile Test CD which has a speaker channel orientation track. It will take you 10 seconds to fugure it.

I would strongly discourage attempting to play a CD on your turntable. Unless I've completely lost touch with the advancements in technology, it will not likely yield the results you need to determine which cable is which channel.

I'm not sure how proficient you are with adjustments to your turntable, but you could potentially determine which connection on the tonearm-cartridge interface is for the right channel, pull that connection (carefully) with a pair of tweezers, and play an LP to determine which is the left. Once you figure that out, it should be pretty easy to figure out which one is the right.

Marco

Play some orchestral music, and look for the violins on the left and the double basses on the right. Almost foolproof.

I would just do a continuity check (ie with a multi-meter) from one of the headshell leads to the RCA. The red headshell lead is the right channel +, green is right channel -. Pick either one, and test to the RCA + or - accordingly. This takes 15 seconds to do.