I prefer light windows with dark menu bar as in High Sierra. However, it seems I can only choose all-dark or all-light in Mojave now. Are there any way to hybrid or customize it?
defaults write -g NSRequiresAquaSystemAppearance -bool Yes
Then logout or restart. Then go to the system preferences and select dark mode. It will make top bar and dock dark while everything else in light mode.
To revert it back:
defaults write -g NSRequiresAquaSystemAppearance -bool No
EDIT: Please also have a look on the answers bellow, they are needed in order to make other parts working, like notification center & spotlight. Run all of the commands, and then logout. Still missing the trash can color :)
defaults write com.apple.Spotlight NSRequiresAquaSystemAppearance -bool No
PS: Remember reboot or logout
Apologies for making a separate answer but I didn't have enough reputation to comment.
The accepted answer works for getting the menu bar and dock to be dark but leaves the Notification Center sidebar really difficult to see. In order to make Notification Center readable again, do:
defaults write com.apple.notificationcenterui NSRequiresAquaSystemAppearance -bool No