The Windows 10 setting windows have a plain white background by default. There are no customization options included on them to switch them to a darker theme. However, you can still do exactly that with this registry trick.
Press the Win key + R to open Run, or press Win + X and select it from that menu. Then enter regedit in Run to open the Registry Editor window shown in the snapshot below.
Next, browse to HKEY_CURRENT_USER \ SOFTWARE \Microsoft \Windows\ CurrentVersion\ Themes\Personalize in the left sidebar. Select Personalize on the left so that you can add a new value to it.
Now you can add a new DWORD value to that key. To do that, you should right-click an empty space on the right of the Registry Editor’s window and select New > DWORD (32-bit) Value. That will add a new DWORD with New Value #1 title as below.
Edit that title by entering ‘AppsUseLightTheme’ in the DWORD text box and press Enter. Then close the Registry Editor window. Right-click the Windows 10 desktop and select Personalize to open the window below, which will now include the new dark theme you added.
You can always switch back to the original theme. Open the Registry Editor again and double-click the AppsUseLightTheme DWORD you added to open the window shown below. Enter ‘1’ in the Value data text box and press OK to close the window. That will remove the dark theme and revert back to the original background.
You might find that Windows 10’s dark mode is better than the default one. It could match your theme’s colors better than the plain white background.