I thought that Squant was a joke… But apparently a woman with the right combination of X chromosome genes would in theory be able to see a fourth channel of color in addition to the usual red, green and blue — a tetrachromat instead of a normal trichromat. She would have two distinct “red” (or “green”) channels, and normal green (or red) and blue channels. That woman wouldn’t even know about her ability, but would probably be extra good at telling colors apart or at matching them. And who knows… maybe one day tetrachromats can have monitors made for them that are capable of displaying Squant after all.