Issues with colors in Photoshop CC

I notice your artboard is 16 bit, what is the document color profile? You can find out here in the Status bar:

If it is other than sRGB, perhaps Photoviewer is not color managed and would render the colors differently because it cannot read the profile.

If that is the case, convert a copy to sRGB and see if the results are better.

Windows Photos is not color managed. It's not supposed to match Photoshop, it never will. Photoshop is right, Windows Photos is wrong.

Color managed means that a monitor profile, which describes very accurately how the monitor displays color, is used to correct the RGB values that are sent to the monitor. This is a standard profile conversion, just like any other profile conversion, only it's done by Photoshop on the fly, as you work, under the covers.

An application that isn't color managed doesn't do this. It just sends the RGB numbers straight through uncorrected.

RGB/hex numbers do not define a color. The color space defines the numbers as a specific color. A color space is e.g. sRGB, Adobe RGB, or your display's native color space. They're all different, and any given RGB triplet produces different actual colors in these different color spaces.

A monitor profile is normally made with a calibrator, by measuring test patches on screen and writing out the results as an icc profile. This profile is a description of the display color space. It doesn't correct anything in itself, it just tells Photoshop's color management module what to do to correct the RGB data for display.

If this is a screenshot, that just confirms my point. A screenshot is in Monitor RGB, which is different from sRGB or Adobe RGB. The same numbers will yield a different color, or conversely, the same color will have different numbers.

To get consistency between the original file and a screenshot of the same, you need to first assign the monitor profile to the screenshot, then convert to whatever standard profile the original file is in.

You may want to switch from your Pantone calibrated profile to Windows sRGB and see if that helps. You'll keep the old profile, it won't be removed. It just won't be the default. Restart your PC after the change.

Likely loading on startup, anyway to disable that in the Smart Manager options or msconfig?

I don't know much about this software, but perhaps their support can set it up for you so you can use it?

Ok, good to know. I can help with Photoshop and sometimes Windows, but third party calibration software does throw in curveballs.