Final answer:
It is true that the trichromatic theory of color vision states there are three types of cones in the eye, each sensitive to different wavelengths of light corresponding to red, green, and blue, enabling the perception of the color spectrum.
Step-by-step explanation:
The assertion that trichromatic theory of color vision posits the existence of three kinds of cones in the human eye is true. This theory is fundamental to understanding how people perceive color. There are three types of cones within the eye, with each type being maximally sensitive to a different wavelength of light. Specifically, S cones are sensitive to short wavelengths (420 nm), M cones to medium wavelengths (530 nm), and L cones to long wavelengths (560 nm). These cones work together to enable the perception of the full spectrum of colors by responding in various degrees to different wavelengths, which the brain then interprets as specific colors.
The accurate color perception results from the combination of these primary colors due to the distinct cones being preferentially stimulated by their respective wavelengths. Therefore, normal-sighted individuals can discern a wide array of hues through this trichromatic process.