Under the new macOS Mojave for the Mac there will be a so-called dark mode, i.e. a layout that displays only dark colors instead of bright ones.
How to activate the dark mode on the Mac with the new macOS Mojave is described in the following instructions:
1. First select the Apple logo in the menu bar at the top of the screen
2. Navigate further to "System settings".
3. Next it goes to "General"
4. You now see the "Appearance" setting
5. Select now as active variant "dark" (instead of light)
This will now activate dark mode on the Mac with macOS Mojave. You will now see mainly dark colors.