Thumb 5 NT, 1988:
Defretted Thumb with neck reprofiled to JD profile (since this photo it's had an ebony unlined board fitted):
JD Thumb made in 1987 - the bass I've had the longest since I bought it at the start of 1988.
Not just the soldering, it looks like there are stray wisps of copper too. I'd desolder each joint, cut off the end of the wire and re-strip the insulation with not too much wire exposed, make sure all the cores are together and resolder it.
I have actually put Dyno labels with "Tx" and "Rx" onto them. However, this requires that the user actually looks at them prior to plugging them back in rather than thinking they remember which is which after unplugging them. And colour coding them would mean having to remember which colour means what, and that's not going to happen.
Reading the manual, you can have TRS stereo from the output socket alone or left channel from the output socket and right channel from the CTR socket, both presumably TRS for balanced output.
I've got about 30 basses, including Seis, Warwicks, and Ibanezezezes, and in that lot is one modified Squier and no Fenders. And I'm perfectly happy with that mix.