In Word, when selecting text to copy or cut, the selection in the past was highlighted with grey shading. Somehow the shading has been changed to black, and completely blocks out the text. How do I change this back to a grey shading?

See https://learn.microsoft.com/en-us/answers/questions/5269743/the-default-selection-color-was-grey-but-it-turns and/or https://learn.microsoft.com/en-us/answers/questions/5202133/how-can-i-change-the-color-which-indicates-the-sel .

It sounds weird, but try this suggestion from https://superuser.com/questions/1522861/microsoft-office-word-selected-text-is-black:

Open Window search bar by pressing Window's flag logo button. Search for Windows Speech Recognition, a little bar will open on top of your screen. Right click the bar and select Off: Do not listen to anything I say Right click the bar again and select Exit It may take a few seconds to work! If it doesn't work at first try repeating the passages above and wait few minutes.