https://arstechnica.com/gadgets/2018/11/to-complement-the-new-windows-10-dark-theme-microsoft-is-adding-a-light-theme/

While end users have been customizing the color schemes of their computers for decades, we've lately seen operating system developers follow their users' lead with built-in, first-party support for dark themes. The dark theme was a big part of the appeal of macOS Mojave, and dark theme support in applications such as Windows Explorer was no less welcome.

With the next feature update of Windows 10, codenamed 1H19 and likely to ship in April next year, Microsoft is going a step further, with the introduction of a light theme. The light theme also comes with a new wallpaper (an iteration of the default Windows 10 wallpaper), and it will brighten up certain areas of the operating system that have always tended be dark regardless of the theme being used.