After my computer sleeps, in certain GTK+ 3 applications, specific colors will not appear:
(Note the blank spaces)
After causing enough unique colors to be drawn, the problem goes away.
Some googling around suggests that this may be related to the
i915 driver for Intel graphics cards, at which point it became apparent that this was the kind of problem that will literally never be fixed.
It was suggested either to add the following incantation to
Section "Device" Identifier "Default Device" Driver "intel" Option "AccelMethod" "UXA" EndSection
or the following in
neither of which, of course, made any difference.
Or, instead of waiting for the impossible to happen I can just run this bit of code:
for i in $(seq 0 255) ; do bash -c 'echo -n $'"'"'\033[38;5;'"$i"'mhi\033[0m'" '" done echo
and then everything is good.