CentOS has not DefaultDepth

Question

In CentOS there is no DefaultDepth line in /etc/X11/xorg.conf file to set the default color depth (although you can add this line to it). How does X determines which color depth to use?

Answer 1

It depends on the driver loaded, and defaults to 8-bit. From the xorg.conf(5) man page (emphasis mine):

DefaultDepth depth

specifies which color depth the server should use by default. The -depth command line option can be used to override this. If neither is specified, the default depth is driver-specific, but in most cases is 8.