Two different phones might have screens that share all the same specs, but in practice they may display colors differently. If you've ever wished you could easily tweak the way those colors are shown, Android N might give it to you. The system UI tuner includes a color calibration menu with sliders for the red, green, and blue channels.

After you activate UI tuner, you'll find the color calibration option in the "Color and appearance" sub-menu. It's on the bare bones side—no included profiles or saved configurations. Just move the sliders and confirm by tapping the box that pops up. If you don't approve the change, your screen will revert to default in ten seconds. That's handy as you can actually set all the colors so low that nothing is visible. The device will fix itself when it times out.

This feature is probably intended for making small tweaks to the color of your display, but you can go way overboard as evidenced by these photos above. The color changes don't show in screenshots, so they're happening at the GPU level, just like Google's new red filter in Night Mode.