So the problem is that under “Personalisation” –> “Colours” the option to “Show the accent colour on the following surfaces” for “Start, taskbar and action center” is greyed out for some reason.

Whatever colors I change, it will not apply to start, taskbar, and action center and they will stay in their default light grey color.

EDIT: I just figured out that if I change the theme back to “Windows” then it will give me the option to change the color of the taskbar. However, once I select a different theme, that option is once more greyed out.

You must have received version 1903 of Windows 10, you cannot change the Taskbar color in the new Windows 10 light theme

Go to Settings – Personalization – Colors

Set Windows default mode to Custom

That should enable you to charge the taskbar color, regardless of whether you set App Mode to light or dark

Please Note, there is another setting you may also like and be unaware of in 1903

For each app, you can now set them individually to light or dark mode – in Settings go to Apps, select an app and choose Advanced Settings, you will find that option there . . .