According to the Young-Helmholtz theory of color vision our cones are specialized at seeing:
a. yellow, blue, and green.
b. green, yellow, and red.
c. blue, green and red.
d. red, green, yellow, and blue.

red, green and blue

Explanation:

The Young–Helmholtz theory (based on the work of Thomas Young and Hermann von Helmholtz in the 19th century), also known as the trichromatic theory, is a theory of trichromatic color vision – the manner in which the visual system gives rise to the phenomenological experience of color. In 1802, Young postulated the existence of three types of photoreceptors (now known as cone cells) in the eye, each of which was sensitive to a particular range of visible light.

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