COLORS OF THE SPECTRUM - DO YOU WONDER WHERE THE YELLOW WENT

The spectrum of white light dispersed by a prism or grating often appe ars as just three main colored bands, red, green, and blue, with yello w barely discernible. When this spectrum is compared with the appearan ce of narrow wavelength bands seen in isolation, the lack of color is surprising. An explanation is offered based on two factors: (1) The ye llow-appearing wavelengths of the spectrum comprise only approximately 5% of the whole and have a luminance comparable with that of the adja cent red and green portions and (2) the response of double-opponent ce lls, observed in the primate visual cortex, could enhance the red and green and obscure the yellow in the spectral image.