This isn't how I view the yellow/green safe word play.
I've never had green as an option given to me before, but for me red is just flat out a safe word, and yellow is a "Ow, I please give me a breather." at least for me.

Like for example if it's getting to the point where I literally just can't take anymore punishment whatsoever because every hit is starting to hurt way too much, i'll use red.
But in the middle of the session I may take a hit in the wrong area (Like a cane that stays a little too low and hits my crown jewels!) i'll say yellow just to let my mistress know I need a pause to recuperate. I don't ever use it more than once a session.

I do like your version of a safeword though. I may float your idea to my mistress if I ever decide to do CBT haha.