Red is an excellent color. Blue is also good, since the red/blue approximately pin the visual octave of radiation.

The problem with a creature both red and blue is that from a distance it would appear purple. A creature with the ability to change color from red to blue might be both advantageous and esthetically/politically appealing. While this can be accomplished by use of chromophores under the surface of the skin, this would mean a relatively thin skin, and we really don't want a thin-skinned creature. One solution would be to have the creature covered with a thick but loose skin in alternate thin stripes of red and blue. Subcutaneous muscles could pull the skin into parallel ridges showing either the red or blue areas as necessary.

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