On the RGB color wheel, "azure" (hexadecimal #0080FF) is defined as the color at 210 degrees, i.e., the hue halfway between blue and cyan. In the RGB color model, used to create all the colors on a television or computer screen, azure is created by adding a 50% of green light to a 100% of blue light.
In the X11 color system, which became a model for early web colors, azure is depicted as a pale cyan or white cyan.
Some languages, such as Italian, generally consider azure to be a basic colour, separate and distinct from blue. Some sources even go to the point of defining blue as a darker shade of azure.<ref>Template:Cite web</ref>
Azure also describes the color of the mineral azurite, both in its natural form and as a pigment in various paint formulations. In order to preserve its deep color, azurite was ground coarsely. Fine-ground azurite produces a lighter, washed-out color. Traditionally, the pigment was considered unstable in oil paints, and was sometimes isolated from other colors and not mixed.
The use of the term spread through the practice of heraldry, where "azure" represents a blue color in the system of tinctures. In engravings, it is represented as a region of parallel horizontal lines, or by the abbreviation az. or b. In practice, azure has been represented by any number of shades of blue. In later heraldic practice a lighter blue, called bleu celeste ("sky blue"), is sometimes specified.
Distinction among indigo, azure, and cyan
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According to the logic of the RGB color wheel, indigo colors are those colors with hue codes between 255 and 225 (degrees), azure colors are those colors with hue codes between 195 and 225, and cyan colors are those colors with hue codes between 165 and 195. Another way of describing it could be that cyan is a mixture of blue and green light, azure is a mixture of blue and cyan light, and indigo is a mixture of blue and violet light.
All of the colors shown below in the section shades of azure are referenced as having a hue between 195 and 225 degrees, with the exception of the very pale X11 web color azure – RGB (240, 255, 255) – which, with a hue of 180 degrees, is a tone of cyan, but follows the artistic meaning of azure as sky blue.
In the Bandai Namco video game series Soulcalibur, one of the main characters, Nightmare, is frequently referred to as the "Azure Knight" due to the azure color of his armor.
Astronomy
The true color of the exoplanet HD 189733b determined by astronomers is azure blue.<ref>Template:Cite web</ref>
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