How can I increase contrast in some internet pages? Sometimes it is quite difficult to go through these pages, as they are grey-and-white instead of common or garden black-and-white.
You can make adjustments system wide. Take a look at the following link. The part under How to change screen gamma using xgamma will probably help you the most. However, if what your experiencing is specific to how your web browser renders web pages, this may not apply.
https://ubuntu-mate.community/t/screen-brightness-too-low-on-pc/15935/2?u=steven
There is also xgamma-gui. It’s old but still works. Just clone or download repository and run XgammaGui