The best thing about the Windows operating system that it lets you customize and tweak it to the fullest extent. Microsoft always offers a decent range of personalization capabilities in its operating system. Starting with version 1903, Windows 10 is finally introducing a system light theme that brings lighter colors for all the visual elements, and the result is a brand-new experience that many users will argue is little similar as the default theme available macOS.
With default settings, Windows 10 1903 uses light mode in Windows 10, you’ll notice the Taskbar, Action Center, Start menu and other elements in the light color scheme. But, Start, taskbar and action center greyed out in Windows 10 Colours Settings
How to fix Start, taskbar and action center greyed out problem in Windows 10 Colors Settings.
In the Personalization settings, click on Themes and then on Windows image under the Themes title.
After completing the steps, Start, taskbar and action center setting box will return to normal state