Solder=old tech that i wont touch. I use RJ45 to DB9 adapters for RS-232.

If i have time to research i will but if not everything gets 23578 connected at both ends. I use a straight RJ45 cable from end to end so it really doesnt matter what the color scheme is but i follow one anyway. If the device isn't being controlled during testing/programming i swap one of the straight RJ45 DB9 adaptors with a 'null pinned" one. This usually gets it working. Occasionally you will run into something different and thats when you have to pull out the manual.

@sig... Usually there is a standard color scheme but i ordered 25 once that had a different color scheme so now i check a few out of each package to make sure they are all the same.