I am running the latest version of LibreOffice under Windows 11 Pro. My formatting marks are a light blue which is difficult to see on the white page background. Is there any way to change the color of these to something easier to see?
“latest version of LO” ???
Releases proceed at different pace across platforms. Consequently “latest version” is meaningless and the actual version may be different tomorrow. You better give the exact version number as reported by Help>About LO.
Some application colours are customisable with Tools>Options, LibreOffice>Application Colors but not the formatting marks.
You could try reducing the brightness of the monitor, most people have brightness too high. There is a tool in Windows to help adjust the display, in the Search field on the Taskbar type Calibrate display and select the Control Panel choice. Step through the app to adjust the display somewhat better than it might be otherwise.
Check to make sure your monitor is not set to a "game* mode
If it is an eyesight issue, you could look at Start Menu > Settings > Accessibility and try some of the settings under Vision.
LCD displays tend to have a very non-linear intensity rendering (in other words they “climb” very quickly from black to white, merging many moderate grey shades with white). It is very difficult to achieve “balanced” rendering without a test-pattern generator. Brightness, contrast and gamma interfere between themselves. As a rule of thumb, brightness sets black level, contrast white level and gamma smooths intermediate tones.
If you have no test-pattern readily available, try this Wikipedia page which offers two grey scales and a gamma zone. Start by the grey samples.
Don’t expect perfect results. Every screen is different due to production dispersion. I can’t tune my two LCD monitors to render the same though they are the same brand and model but they were bought on different dates and don’t come from the same batch. Calibration is easier with CRTs but they have almost disappeared.