I don't know if this is an error in the book or merely the review:
(Trichromacy is absent in people with red-green color blindness, who are born with two functional color receptors instead of three.)
Most of the colorblind are anomalous trichromats. The have three types of cones, but one is either weak or the red and green are too close in wavelength which weakens color perception.

This picture was taken near Moscow in 1910. It was made by taking 3 pictures . Each one with a different color filter then combining all 3.