very good points from many here
Talked with friends about the very same as late as yesterday, especially because so many of the new superlightweight carbon bars we use for mostly foiling now, dont have any colour coding whatsoever, just all black.
Have had many different colours on my bars, but I dont find they, or the line colours themeselves, are any good for fast reckognition of right/left as in the dark or rainy weather or whatever just when slightly in doubt, you can not distinguish for sure which side is which in my experience.
I was motivated by one having a "funny" kind of small flag on one line, an ad or commercial I think, still dont know why it was there, but today I made a small one out of spinnaker tape.
My thought is, that it will be way faster and easier to see, than colours.
Sailed with it today, and it did not disturb anything.
Whether you want it to the left or right is personal of course.
Just an idea?
Regarding when you try friends kites, this is not an issue, as you know they can be turned "any" way, two of my friends just put the lines up, sometimes in reverse red lines to the right, but you can get used to that pretty fast.