Sets whether or not PyMol renders shadows casted onto labels and whether or not the labels themselves cast shadows.
set label_shadow_mode, 0 # turn off shadows projected onto lables, turn off shadows cast from labels
set label_shadow_mode, 1 # turn on shadows projected onto labels, turn off shadows cast from labels
set label_shadow_mode, 2 # turn off shadows projected onto lables, turn on shadows cast from labels
set label_shadow_mode, 3 # turn on shadows projected onto lables, turn on shadows cast from labels