I build emacs without-toolkit-scroll-bars and I've had this in my ~/.emacs for ages:
(set-face-background 'region "LightSteelBlue")
(set-face-foreground 'scroll-bar "LightSlateGray")
(set-face-background 'scroll-bar "Gray90")
After upgrading to 28.1, the first and last lines work, but the scroll-bar foreground does not. It remains black.
Here's the strange part. If I execute that line manually after startup, nothing happens. But if I first set it to white manually, then it does work:
(set-face-foreground 'scroll-bar "white")
(set-face-foreground 'scroll-bar "LightSlateGray")
However, that only works if I do it manually. If I put those two lines at the end of my ~/.emacs, it doesn't work and I still have a black scrollbar.
It's not a huge deal but I do wonder what's going on.