There are quite a few ways to customize and activate light mode on Windows 10 v1903, and here is how ... as they were already (Light App Mode and Dark Windows Mode), it can be achieved via ...

Switching between light and dark themes across Windows 10 has provided consistency issues with the overall visual appearance. While almost all first party software, including the Calculator app ...

but the new take on the Dark theme seems to have been heavily inspired by photography. It looks like the browser makers intend to reduce the light in a photo to a minimum while retaining contrast.