Color numbers changing moments after setting (Photoshop, Illustrator, Fresco)
I'm doing a series of digital paintings in Adobe Fresco that will eventually be printed in a book. I'm working on choosing key colors for the project that will print well once they're converted from RGB to CMYK. I prefer working with the HSB model within the RGB color space. I would work directly in CMYK, but Fresco only does RGB, so I know the final conversion is on me and I'm paying attention to gamut warnings by selecting colors in Photoshop first.
Problem is, the colors I choose aren't "sticking!" For example, one of my desired key colors is Hue 189, Saturation 100, and Brightness 85, which is about as bright a teal as I can go before getting a gamut warning. I'll select those values in the color picker, paint, and then do something else, like erase or paint with a different color. When I again click on the teal swatch or sample the color I already laid down, I'll find the values in the color picker have changed! Again and again it will revert to something similar but just different enough, e.g. HSB 186-100-84. This happens in Fresco, Photoshop, and Illustrator. It happens with every hue I've tried. And it sometimes results in a color being out of gamut! I've worked with the Adobe suite for 15+ years and I've never seen this behavior. What is going on here?

