This page deals with slang terms for a Zombie apocalypse, in the heat of the moment it's easy to garble in horror at the situation and important messages are lost so easy terms are introduced by the military which are inevitably adopted and mutated by civilians.
In art, an underpainting is an initial layer of paint applied to a ground, which serves as a base for subsequent layers of paint. Underpaintings are often monochromatic and help to define colour values for later painting.
Dead-color (in Dutch dood-verf), which is the equivalent of today's term  underpainting , is a more or less monochrome version of the final painting intended to give volume, suggest substance to form, fix the composition and distribute darks and lights with a good degree of accuracy.