Which of the following is NOT a color opponent channel according to the color opponency theory?

In color opponency theory, the visual system processes color information through pairs of opposing colors. The key channels identified within this theory include red/green, blue/yellow, and black/white. Each of these pairs represents a contrast mechanism whereby the activation of one color inhibits the perception of its opponent.

The red/green channel signifies that the presence of red colors increases the perception of red while simultaneously inhibiting the green perception, and vice versa. Similarly, the blue/yellow channel operates on a contrasting basis where blue inhibits yellow and vice versa. The black/white channel pertains to the processing of brightness and luminance.

The option indicating blue/green does not represent a recognized color opponent channel. Blue and green are not typically processed in a manner that suggests opposition in the same way as the established channels. Instead, they are usually perceived in conjunction with one another rather than in opposition, which is why this option is identified as the one that does not belong to the color opponent channels outlined by the theory.