I would like to set the colour depth of my antiX installation to something easier for my hardware to keep up with. How do I check and alter this setting? Are there themes for an 8-bit colour depth setting?

The answer appears to be to change the xorg.conf file in /etc/X11 which must be done as root user. However, I changed the depth to 8 bits and the terminal became unusable. It just showed an entirely black window with no prompt. I'm pretty sure 8-bits should be plenty to display all the colours needed. Returning to 16-bit fixed the problem. Does anyone know how to make 8-bits work?

twiddling the conf has been so infrequent that I haven't retained a clear memory of the details ~~ I must revisit the docs each time

manpages:
man xorg
man xorg.conf

forum search:
conf xorg

Create a backup of xorg.conf before editing, so that you might later revert any changes, right

Are there themes for an 8-bit colour depth setting?

themes, themes, and... themes.
Several of your posts have mentioned themes.
@8-bit, or 16-bit ort... everything is rendered the same, handled the same, globally.
There's no reason to suspect that any given them would be functionally problematic when rendered at 8-bit.
You might notice that certain elements of a given theme are unsightly (banded, due to gradient dithering) or, if you are affected by color blindness, you may discover that some adjacent onscreen elements (checkbox vs background) are difficult to discern when a particular theme is in effect.

box-look.org
Some dee-ziners might advertise whether or not they have tested a given theme @8bit, and if so, might provide screenshots showing what result to expect for their theme(s) when rendered @bit.

This is with the theme ClearView Glass Medium with colour depth set to 8-bit in xorg.conf



The image below is with the colour depth set to 16-bit.



If the theme is not to blame, have you any idea what is? The GTK2"look and feel"? That's currently set to Thin Ice.