The dark theme in macOS applies to the entire interface. Not only are the apps converted to a dark grey, the menus, the menu bar, and the dock are also given a darker color. The implementation of the dark theme in macOS is great but still, not everyone likes all aspects of it. If you’d like to get a dark menu bar and dock with the light theme on macOS, you can get it with a little terminal command.
Dark menu bar and dock with light theme
Open the Terminal by tapping the Command+Space bar keyboard shortcut to bring up Spotlight search. Type Terminal and select the app result. In Terminal, enter the following command, and tap the Enter key.
defaults write -g NSRequiresAquaSystemAppearance -bool Yes
The command completes in a split second. Once it does, log out and log back in again. To log out, go to the Apple menu, and select Log out.
When you log back in, you will need to change the theme. Open System Preferences and go to the General preferences. Select the Dark theme under Appearance.
After you apply the dark theme, the menu bar and the dock will turn dark grey but everything else e.g., the Finder, System Preferences, Safari, etc., will be light/grey-white.
If you want to undo this UI change, you will need to run another command in the Terminal. Open Terminal and run the command below;
defaults write -g NSRequiresAquaSystemAppearance -bool No
You will need to log out, and log back in. When you log back in, the themes that you select will be applied in their entirety. If you apply the Light theme, the menu bar and the dock will also be light along with everything else. If you select the Dark theme, everything, including the menu bar and dock will be dark.
Regardless which theme you’ve applied, and whether or not you’ve applied in full or partially, the transparency effect can still be enabled or disabled. Additionally, you can still set any accent color of your choice even if you apply the theme partially. This doesn’t work the other way i.e,., you cannot enable a light menu bar and dock but apply the dark theme to everything else.
Apple has restricted theme modifications quite a bit so there isn’t much else you can do with the menu bar other than get a light or dark one. There is, as yet, no way to apply the accent color to the menu bar or to the dock.