Impossible color
![The human eye's red-to-green and blue-to-yellow values of each one-wavelength visible color](/Images/godic/202501/01/Color_perception.svg2636.png")
![The CIE 1931 color space chromaticity diagram. The white regions correspond to imaginary colors.The ProPhoto RGB color space uses imaginary green and blue primaries to obtain a larger gamut (space inside the triangle) than would be possible with three real primaries. However, some real colors are still irreproducible.](/Images/godic/202501/01/CIExy19312636.png")
![](/Images/godic/202501/01/CIExy1931_ProPhoto.svg2636.png")
![Normalized spectral sensitivity curves of the three kinds of cone cells, which define the space of human color sensation](/Images/godic/202501/01/Cones_SMJ2_E.svg2636.png")
Impossible colors or forbidden colors are supposed colors that cannot be perceived in normal seeing of light that is a combination of various intensities of the various frequencies of visible light, but are reported to be seen in special circumstances.