MUST NOT FIRE. Black on white is 21 to 1.
MUST NOT FIRE. 767676 on white is 4.54 to 1, just over AA.
MUST FIRE. 999999 on white is 2.85 to 1.
MUST FIRE via alpha compositing. Black at 35 percent over white.
MUST FIRE. Dark green text on a dark green ancestor.
MUST FIRE. Grey text over a translucent layer on dark green.
MUST NOT FIRE. Large text needs only 3 to 1.