It's not entirely about bit depth. Think about 1 bit of a given colour light, it can turn on or off, but the bit depth doesn't tell us anything about the colour of the light it is turning on or off.

Encoding in a larger volume colour space may require additional bit depth to prevent posterization, but that's somewhat tangential. The larger issue is the number of vendors and operating systems that can't get it right. Windows is horrific, for example, with Android being at least as bad, as given by the accounts in the comments here.