This goes beyond just inverting pixel colors, which is already possible in iOS.
Milen Yanachkov on phoneArena suggests “Don’t just invert whites, also subdue and limit other colors as much as possible. For example, instead of using solid, colorful toggles for various settings when they are enabled, a colorful outline can convey just as much information, without emitting unnecessary light.”
Yanachkov produced multiple images with his recommendations. Some of these are layered on renders of the iPhone XI created from various rumors about this upcoming model.
Dark mode and iOS 13
Apple added a system-wide dark mode to macOS Mojave, and unconfirmed reports indicate it’s doing to same with the next version of iOS. That order is somewhat surprising, as iPhone models will benefit more than Macs. from this change. Each pixel on an iPhone’s OLED screen glows individually with no need for a backlight, so they use less power when displaying darker colors.
No matter the type of display, studies have shown that dark mode is less fatiguing to look at for long periods, and it’s less disruptive to the viewer’s sleep cycle.