[Kamshak]

I think they say this specifically, grey is better to distinguish shadows but if you want to conserve energy you can go with true black.

> UIs that require efficient battery usage can use true black. In these cases, some devices (such as wearables with OLED screens) can turn off any pixels that display black to conserve battery power.

[soulofmischief]

...I feel like all UIs should require efficient battery usage, and UIs that don't are an anti-pattern.

[marcusjt]

Yes but whether dark is more efficient or not depends on screen technology, plus there's battery level, viewing conditions and user preferences to factor in, so ultimately it's up to the phone OS / supporting software to make smart decisions about what's the right theme to show at any given moment.

[soulofmischief]

That seems a bit orthogonal to my statement.

Regardless of specific hardware implementations, it can be agreed upon that patterns which can cause some non-negligible amount devices to be less energy efficient are anti-patterns.