I don't know why I've never ran across this issue before, I've replace lots of turn signal cancel springs over the years, GM vintage 70s and 80s vehicles, and always just said red or blue spring when I needed one. The actual part numbers are 1964784, and 1964785. The problem is, the red ones are listed in the parts book as 1964784, right side. And the blue ones are 1964785, left side. But every time a left turn signal won't cancel, the red spring is broken. Which is listed as a right spring. And if the right side won't cancel, the blue spring is broken, which is listed as a left spring.

What am I missing here?

Perhaps the "left" and "right" refer to the direction the steering shaft is rotating in order for the cancel to actuate?

I suppose that'* possible. I'm hoping for a definitive answer from someone that has an explanation to why this might make sense. Everyone I know who has replaced these springs seems to be baffled too.