Purple - Purple Versus Violet

Purple Versus Violet

Violet is a spectral color (approximately 380–420 nm), of a shorter wavelength than blue, while purple is a combination of red and blue or violet light. The purples are colors that are not spectral colors – purples are extra-spectral colors. In fact, purple was not present on Newton's color wheel (which went directly from violet to red), though it is on modern ones, between red and violet. There is no such thing as the "wavelength of purple light"; it only exists as a combination.

Pure violet cannot be reproduced by a Red-Green-Blue (RGB) color system, but it can be approximated by mixing blue and red. The resulting color has the same hue but a lower saturation than pure violet.

One interesting psychophysical feature of the two colors that can be used to separate them is their appearance with increase of light intensity. Violet, as light intensity increases, appears to take on a far more blue hue as a result of what is known as the Bezold-Brücke shift. The same increase in blueness is not noted in purples.