You can change the Start menu to any custom color you want, but that will, by default, change the Taskbar to the same color.
When you create a calendar, it takes up a default color available in the color palette of Google Calendar. This color is applied to all the events you create within the calendar. However, you can ...
Open the Windows Settings via the Start menu and click on Personalization and then Colors. In the menu next to Select Mode, set the option Custom and change Select Default Windows mode to Dark–you can ...