Maybe I'm missing something obvious enough here, but you need to check each instrument that the magnetometer is supposed to be connected to.
I.E., an rs-232 tx on the magnetometer should be connected to an rs-232 receive on whatever instrument it's supposed to be connected to. The color is not an automatic guide because it really depends on what it's plugged into on the other end. The color of the wire is a guide to assure you that you're working with the correct wire from the other connected end once you've identified it.
As you do each wire, you can then write down the color to remind you during future maintenance. Personally, I like to put a small tag on each wire to remind me of which pin it's going into.
Tom