New Android builds often include accessibility features, and it seems Android 12 is no exception - apparently it will let you choose your own system color, which applies to all apps and menus.
This comes from 9to5Google, which acquired a small amount of information on the upcoming feature. The rumor says you'll be able to choose one main and one 'accent' color, and these will work with native apps and menus, as well as compatible third-party apps if the developers allow.
According to the information, it's possible when brands adapt Android for their phones, they'll introduce brand-specific color schemes to choose from. It doesn't seem you'll be able to introduce your own color-scheme, so you'd have to pick from one the phone company does, but we'll have to see how many options each phone has.
Why this feature is useful
If this feature does make its way to Android phones, the obvious key use case is customization. You'll be able to pick your favorite colors and have much of the phone adorned in these shades.
Accessibility is another key selling point too, though. People with particular vision issues, like types of red-green or blue-yellow color blindness, could possibly tweak the way their phone looks, so they can easily distinguish between the shades.
Dark or light modes do this already for some people, but the ability to actually change the colors shown would let people tweak their phone's settings to suit their individual vision issues. This would also provide more consistency given dark modes can be different between phones and even apps.
We'll have to see if this feature does make its way to Android 12 - sometimes Android features get rumored but aren't actually coming after all, or are being worked on, but get dropped by Google for various reasons. Android 12 will likely get unveiled in the coming months, with an early beta launched ahead of a full roll out near the end of 2021.