Final answer:
The opponent-process theory pairs are black-white, blue-yellow, and red-green, making orange-blue the incorrect pair that does not fit into this theory.
Step-by-step explanation:
The opponent-process theory of color vision describes how colors are coded in pairs within the visual system. These pairs are characterized by cells that are excited by one color and inhibited by the complementary color. According to this theory, valid opponent pairs are black-white, blue-yellow, and red-green. Therefore, the pair that does not represent a complementary system in the opponent-process theory is orange-blue, as this is not one of the identified opponent pairs.