Favourite Colour

Purple is a range of hues of colour occurring between red and blue.  The Oxford English Dictionary describes it as a deep, rich shade between crimson and violet.
In the ancient world, purple was the colour worn by Roman Emperors and magistrates, and later by Roman Catholic bishops. Since that time, purple has been commonly associated with royalty and piety. The word 'purple' comes from the Old Englosh 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 English was in the year 975 AD.

In the traditional colour wheel used by painters, violet and purple are both placed between red and blue. Purple occupies the space closer to red, between crimson and violet.  Violet is closer to blue, and is usually less intense and bright than purple.While the two colours look similar, from the point of view of optics there are important differences. Violet is a spectral, or real colour – it occupies its own place at the end of the spectrum of light, and it has its own wavelength (approximately 380–420 nm). It was one of the colors of the spectrum first identified by Isaac Newton in 1672, whereas purple is simply a combination of two colours, red and blue. There is no such thing as the "wavelength of purple light"; it only exists as a combination
Pure violet cannot be accurately reproduced by the Red-Green-Blue (RGB) color system, the method used to create colours on a television screen or computer display. It is approximated by mixing blue light at high intensity with less intense red light on a black screen. The resulting colour has the same hue but a lower saturation than pure violet.

One curious psychophysical difference between purple and violet is their appearance with an increase of light intensity. Violet, as it brightens, looks more and more blue. The same effect does not happen with purple. This is the result of what is known as the Bezold- Brucke shift. While the scientific definitions of violet and purple are clear, the cultural definitions are more varied. The colour known in antiquity as Tyrian purple ranged from crimson to a deep bluish-purple, depending upon how it was made. The colour called purple by the French, pourpre, contains more red and half the amount of blue of the colour called purple in the United States and the U.K. In German, this colour is sometimes called Purpurrot ("purple-red") to avoid confusion.

Purple, unlike violet, is not one of the colours of the visible spectrum. It was not one of the colours of the rainbow identified by Isaac Newton, and it does not have its own wavelength of light. For this reason it is called a non-spectral color. It exists in culture and art, but not, in the same way that violet does, in optics. It is simply a combination, in various proportions, of two primary colours, red and blue. In colour theory, a "purple" is defined as any non spectral colour between violet and red (excluding violet and red themselves). The spectral colours violet and indigo are not purples according to colour theory but they are purples according to common English usage since they are between red and blue.

In the traditional colour wheel long used by painters, purple is usually placed between crimson and violet.  In a slightly different variation, on the colour wheel, it is placed between magenta and violet. This shade is sometimes called electric purple (See shades of purple). In the RGB colour model, named for the colours red, green and blue, used to create all the colours on a computer screen or television, the range of purples is created by mixing red and blue light of different intensities on a black screen. The standard HTML colour purple is created by red and blue light of equal intensity, at a brightness that is halfway between full power and darkness. In colour printing, purple is sometimes represented by the colour magenta, or sometimes by mixing magenta with red or blue. It can also be created by mixing just red and blue alone, but in that case the purple is less bright, with lower saturation or intensity. A less bright purple can also be created with light or paint by adding a certain quantity of the third primary colour (green for light or yellow for pigment).

On a chromaticity diagram, the straight line connecting the extreme spectral colours (red and violet) is known as the line of purples (or 'purple boundary'); it represents one limit of human colour perception. The colour magenta used in the CMYK printing process is near the center of the line of purples, but most people associate the term "purple" with a somewhat bluer tone, such as is displayed by the colour "electric purple" (a colour also directly on the line of purples), shown below. Some common confusion exists concerning the colour names "purple" and "violet". Purple is a mixture of red and blue light, whereas violet is a spectral colour. On the CIE xy chromaticity diagram, violet is on the curved edge in the lower left, while purples are on the straight line connecting the extreme colours red and violet; this line is known as the line of purples, or the purple line.

Grapes, eggplants, pansies and other fruits, vegetables and flower are purple because they contain natural pigments called Anthocyanins. These pigments are found in the leaves, roots, stems, vegetables, fruits and flowers of all plants. They aid photosynthesis by blocking harmful wavelength of light that would damage the leaves. In flowers, the purple Anthocyanins helo attract insects who pollinate the flower. Not all Anthocyanins are purple; they vary in colour from red to purple to blue, green or yellow, depending upon.