I want to calibrate my desktop. I managed to find the colour option in the settings menu, but the calibrate button it's greyed. How to activate it so I can calibrate my colours?
This button is not for manual calibration. To calibrate a monitor, you need a special device called colorimeter.
If you don't own such a device, the best thing you can do, is to do a websearch for available color profiles you can try (try, because not every panel is the same, so someone else's color profile for your monitor might make things even worse).