Not sure if this means anything, but I was subtitling on PP last night when a new version came in (22.4.0 b57). When I went back to subbing the color of the boxes in the timeline had changed from mango to lavender. I went to check on the assigned color in label defaults and saw "captions" was set on mango. I tried changing it but the color wouldn't change. For whatever reason I changed "still" to mango and the color of the caption went back to mango. Not sure what this means, but there you go.
I would call this a bug. For some reason, in the current (22.4.0), PR is seeing Captions as stills. In previous versions, Captions are defined in preferences as a Mango colored label. "Stills" are Lavender. And yes, if you change the Stills color, captions change. Captions should be the Captions color, not stills.
I can change the "Captions" in labels, but Captions don't change unless you change the Stills color.
Beta 22.5.,0 Build 25, shows Captions correctly.
Yes, it is just a label color,and should not actually affect captions or exports.