Line of purples

Rather, every color on the line is a unique mixture in a ratio of fully saturated red and fully saturated violet, the two spectral color endpoints of visibility on the spectrum of pure hues.

Unlike spectral colors, which may be implemented, for example, by the nearly monochromatic light of a laser, with precision much finer than human chromaticity resolution, colors on the line are more difficult to depict.

For example, in the CIE XYZ it is a planar sector bounded by black–red and black–violet rays.

The boundary of sRGB (pictured) runs approximately parallel to the line, connecting the primaries red and (color wheel) blue, and thus purples near the line are absent from the gamut of sRGB.

Magenta ink, which is one of CMYK's primaries, is also very distant from the line for the reason explained above.