Very Computer

I just installed RedHat 6.1, and every xterm window now comes up
gray-on-gray, white-on-white, or some other unreadable color combo.  It
doesn't matter if I try gnome-terminal, xterm, nxterm, or rxvt.  I try
changing Settings|Preferences|Colors in the gnome-terminal menu, to no
effect.  Changing from Enlightenment to twm as my window manager also
doesn't fix the problem.  This makes the system nearly unusable, since so
much needs to happen at a term prompt.  Anybody have any ideas?

Sounds weird. Maybe some setting in .Xdefaults - or lack of it.
At at least it should be possible to mend the situation there.

Try paste this line into a terminal window and give an enter, just to
see if it's at all possible to get other colors:

rxvt -sr -fn fixed -bg black -fg white &

Did that look more or less usable? If so - read on.

.Xdefaults contains settings for "Xterm and family" - like rxvt.

You should have .Xdefaults file in your homedir. You could try add these
lines there:

XTerm*Background: Black
XTerm*Foreground: Grey
XTerm*pointerColor: White

These are of course just suggestions - tune to your likings. For valid
color-names see usr/X11R6/lib/X11/rgb.txt.

For syntax: There's a "zillion" parameters you can tune in .Xdefaults -
far as Xterm goes see the manpage (man xterm).

If you're happy with the approach above, as root: also edit the
/etc/skel/.Xdefaults file - that way other users you create will
"Inherit" the same setting for their own homedir's initial .Xdefaults
file.

K.