Black and yellow (strongest primary combination).
Black and red.
Black and light blue.
Black and green.
Black and orange.
Red and dark blue.
Red and green.
Red and yellow.
Light yellow and dark blue.
Blue and orange.
(A white letter used with any of the above will give a three color effect
with two printings.)
In combination with black the density and richness of the other colors
will be intensified in the effectiveness of the display. Where black is
laid over the supplementary colors it often gives the effect of an added
color.