Perhaps everyone perceived color slightly differently; perhaps even people with normal vision had different interpretations.
Thus, interaction between at least two types of cone is necessary to produce the ability to perceive color.
The eye has three sets of cones that perceive color: one sensitive to blue light, one to green and one to red.
Part of the problem with this definition is that the human eye does not simply analyze the frequencies of incoming light when it perceives color.
Someone able to perceive color, as you called it?
Even when presented with this information, the patient believed he had retained his ability to perceive color even though the world around him appeared grey.
The photo-receptors by which the eye perceives color correspond more closely with the additive process.
He also perceives light and color where adults see only drabness.
Even though there are attempts to classify consumer response to different colors, everyone perceives color differently.
It strikes many of us, though, that those supposedly sophisticated social meters fail when they perceive color.