I’m going to try to summarize and clarify:
I think people are mostly talking about the hue bar at the bottom of the tint/shade/tone picker. There are a few posts across Steam and social media platforms, though, and without a picture it’s not always obvious.
If there were changes to spectrum, for whatever reason, I haven’t seen as many reports.
In earlier releases, shader-based color pickers had a red-gray problem. See this thread. Hue is undefined when saturation is zero, but throwing exceptions is frowned upon. The hue becomes zero instead. Gray is red (or whatever hue is at zero in the color model).
The shader toggle workaround relied on old code being inconsistent with newer shader code. As the two were made more consistent in subsequent releases, the workaround stopped working.
As far as I know, there is still a problem with discrete normal maps. The shader toggle workaround still works in this case.
Depending on whether someone is using the stable version, the beta version or a version built from Github source code, the timeline for these changes will vary.