Purple is a color intermediate between red and blue. It is similar to violet, but unlike violet, which is a spectral color with its own wavelength on the visible spectrum of light, purple is a composite color made by combining red and blue. According to surveys in Europe and the U.S., purple is the color most often associated with royalty, magic, mystery and piety. When combined with pink, it is associated with eroticism, femininity and seduction.
Purple was the color worn by Roman magistrates; it became the imperial color worn by the rulers of the Byzantine Empire and the Holy Roman Empire, and later by Roman Catholic bishops. Similarly, in Japan, the color is traditionally associated with the Emperor and aristocracy.
Etymology and definitions
The word 'purple' comes from the Old English word purpul which derives from the Latin purpura, in turn from the Greek πορφύρα (porphura), name of the Tyrian purple dye manufactured in classical antiquity from a mucus secreted by the spiny dye-murex snail.
The first recorded use of the word 'purple' in the English language was in the year 975 AD. In heraldry, the word purpure is used for purple.
Purple vs. violet
In the traditional color wheel used by painters, violet and purple are both placed between red and blue. Purple occupies the space closer too red, between crimson and violet. Violet is closer to blue, and is usually less saturated than purple.
While the two colors look similar, from the point of view of optics there are important differences. Violet is a spectral color – it occupies its own place at the end of the spectrum of light first identified by Newton in 1672, and it has its own wavelength (approximately 380–420 nm) – whereas purple is a combination of two spectral colors, red and blue. There is no such thing as the "wavelength of purple light"; it only exists as a combination.
Monochromatic violet light cannot be produced by the red-green-blue (RGB) color system, the method used to create colors on a television screen or computer display (a fact that is, indeed, true of any monochromatic color of the spectrum besides the shades of red, green, and blue chosen for the primaries).
However, the system is capable of approximating it due to the fact that the L-cone (red cone) in the eye is uniquely sensitive to two different discontinuous regions in the visible spectrum – its primary region being the long wavelength light of the yellow-red region of the spectrum, and a secondary smaller region overlapping with the S-cone (blue cone) in the shortest wavelength, violet part. This means that when violet light strikes the eye, the S-cone should be stimulated strongly, and the L-cone stimulated weakly along with it. By lighting the red primary of the display weakly along with the blue primary, a relatively similar pattern of sensitization can be achieved, creating an illusion, the sensation of extremely short wavelength light using what is in fact mixed light of two longer wavelengths. The resulting color has the same hue as pure violet; however, it has a lower saturation.
In the Roman Catholic church, cardinals wear red and bishops wear purple