B) herman von helmholtz The trichromatic color theory<span> began in the 18th century, when </span>Thomas Young<span> proposed that color vision was a result of three different </span>photoreceptor cells<span>. </span>Hermann von Helmholtz<span> later expanded on Young's ideas using color-matching experiments which showed that people with normal vision needed three wavelengths to create the normal range of colors. Physiological evidence for trichromatic theory was later given by </span>Gunnar Svaetichin<span> (1956).</span>
