After upgrading my monitor to 4k display with wider color-gamut, started
Xorg with 30-bit color depth (DefaultDepth 30 in '/etc/X11/xorg.conf').
'xdpyinfo' also reports:
depth of root window: 30 planes

Most of the other softwares I use displays without any problem.
However, 'gv FILE.ps' kept on waiting for the file to open.
To understand the issue in opening the file, I tried 'ghostscript FILE.ps'.
It showed the following:

GPL Ghostscript 10.05.1: Unsupported X visual depth: 30
**** Unable to open the initial device, quitting.
Segmentation fault

Given that most of the present era monitors support 10-bit colour for
R/G/B, more and more people are going to be hit by this lack of
support. Therefore, I am marking this as 'important'.
Upstream bugs also do not list this issue.