LRC 15.2.1 OS Windows 11 when selecting edit in Photoshop the image opens as black and white. I have checked all my export settings. I have uninstalled and reinstalled this fixed it temporarily but the issue has now returned.

If you view the image at 100% in both LrC and PS, is there still a difference?

If there is, and you have an Nvidia GPU, make sure that you’re using the Studio driver, not the Game ready driver.

This could also be caused by a defective or incompatible monitor profile.
Try setting it to sRGB (use Adobe RGB if you have a wide gamut monitor).

Close LrC and PS.
Go to Control panel > Color Management.
Add the sRGB (or Adobe RGB) profile, then set it as Default.
If this fixes the issue, you should ideally calibrate your monitor with a hardware calibrator.
This will also create and install a custom monitor profile that will be more accurate than sRGB.

Please post a screenshot of this image in LrC.

Very strange. I’ve never heard about such issue.

Do you have tried to reset the Lightroom Classic preferences to the default settings?

Makes it any difference if Photoshop runs in the background when you send a image form LrC to Ps of PS must start first?

This is very strange.
Is it happening to one particular image, or all images you send to Photoshop  for editing?
When you move the mouse pointer across the image, are all R, G, and B values identical in the Info panel?

Please post a screenshot of the entire Photoshop window with an image open and the History panel and Info panel visible and expanded.