disable all colors (in auc-tex) once running

[ivowel]

dear emacs experts---on some of my terminals, the background color is
not white.  this can make it hard to see the lighter colors, esp in
syntax coloring mode.

I have tried to put (setq-default  global-font-lock-model nil) into
my .emacs file, but this does not seem to have an effect.

is there a way to define a key that toggles between no-coloring
(syntax) mode and coloring mode?

sincerely,

/iaw