Microsoft added an updated Dark Theme for file explorer that is for the most part usable. Windows 10 1809 you can set up a dark mode for file explorer. Windows 10 introduces a new dark theme for the classic version of File Explorer, which anyone can enable using the “Colors” page from the “Personalization” settings page. The new dark theme coats with different shade of black the background, pane, ribbon and file menus, context menus, and popup dialogs
Enabling the Dark Theme in File Explorer and Windows 10
To enable the file explorer dark theme, head to Settings > Personalization > Colors. Then scroll down in the right column to the more options section and choose dark for the “Choose your default app mode” option.
Once you’ve completed the steps, open file explorer, and you should now see the dark theme. The Dark Theme will be enabled in all support applications and interfaces, including in file explorer.
Note: Dark theme on Windows 10, unless you’re running 1809 or above, file explorer doesn’t change with it.