8 bit and 16 bit in CMYK Color

See: http://digitaldog.net/files/TheHighBitdepthDebate.pdf

True for RGB or CMYK.

Oh and bit depth doesn't equal colors FWIW, this is the encoding of color values, not necessarily colors (which we must be able to see):

http://digitaldog.net/files/ColorNumbersColorGamut.pdf

The colour mode - RGB or CMYK describes how the colour is stored for each pixel. In the case of RGB it is a value for Red, one for Green and one for Blue. In CMYK it is one for Cyan, one for Magenta one for Yellow and one for Black.

The bit depth 8 bit 16 bit or 32 bits/channel is the number of bits used to store each value. So in 8 bits/channel there are 256 possible values. In 16 bits/channel there are 65536. That does not give a larger range, just a larger number of steps across the same range.  32 bit/channel is a bit different in that it does extend the range so each value can be darker than the darkest displayed black or whiter than the whitest displayed white. It is a specialist mode for HDR (High Dynamic Range) and not needed for normal images.

There is a third element that needs to be considered and that is the colour profile. There is no generaic RGB and generic CMYK. The way in which the values at each pixel represent actual colours is described in the document colour profile. That is why when someone asks for a document to be in CMYK it is essential to know which CMYK profile. Without that information the values are meaningless.

Dave