That has fixed the problem, although I didn’t add it to my Child theme, I added it to the Customization section under additional CSS.
This is the code that sorted it out.
opacity: 0.5 !important;
background-color: cyan !important;
I guess I should look at the Child Theme next, if your code changes after every update… 😉
Thanks again for your help.
This can be assigned to RESOLVED.