Web colors are colors used in designing web pages, and the methods for describing and specifying those colors.
Authors of web pages have a variety of options available for specifying colors for elements of web documents. Colors may be specified as an RGB triplet in hexadecimal format (a hex triplet); they may also be specified according to their common English names in some cases. Often a color tool or other graphics software is used to generate color values.
Web colors have an unambiguous colorimetric definition, sRGB, which relates the chromaticities of a particular phosphor set, a given transfer curve, adaptive whitepoint, and viewing conditions. These have been chosen to be similar to many real-world monitors and viewing conditions, so that even without color management rendering is fairly close to the specified values. However, user agents vary in the fidelity with which they represent the specified colors. More advanced user agents use color management to provide better color fidelity; this is particularly important for Web-to-print applications.
A hex triplet is a six-digit, three-byte hexadecimal number used in HTML, CSS, SVG, and other computing applications,
to represent colors. The bytes represent the red, green and blue components of the color. One byte represents a number in
the range 00 to FF (in hexadecimal notation), or 0 to 255 in decimal notation. This represents the least (0) to the most (255)
intensity of each of the color components. The hex triplet is formed by concatenating three bytes in hexadecimal notation, in
the following order:
Byte 1: red value (color type red)
Byte 2: green value (color type green)
Byte 3: blue value (color type blue)
For example, consider the color where the red/green/blue values are decimal numbers: red=36, green=104, blue=160 (a greyish-blue color).
The decimal numbers 36, 104 and 160 are equivalent to the hexadecimal numbers 24, 68 and A0 respectively. The hex triplet is obtained
by concatenating the 6 hexadecimal digits together, 2468A0 in this example.
Note that if any one of the three color values is less than 16 (decimal) or 10 (hex), it must be represented with a leading zero so
that the triplet always has exactly six digits. For example, the decimal triplet 4, 8, 16 would be represented by the hex digits 04, 08,
10, forming the hex triplet 040810.
The number of colors that can be represented by this system is
256 times 256 times 256 = 16,777,216 colors
Converting a decimal RGB value to a hexadecimal value is fairly straightforward. RGB values are usually given in the 0-255 range; if they are in the 0-1 range, the values are multiplied by 255 before conversion. This number divided by 16 (integer division; ignoring any remainder) gives us the first hexadecimal digit (between 0 and F, where the letters A to F represent the numbers 10 to 15. The remainder gives us the second hexadecimal digit. For instance the RGB value 201 divides into 12 groups of 16, thus the first digit is C. A remainder of 9 gives us the hexadecimal number C9. This process is repeated for each of the three color values. Most modern operating systems have a built-in calculator to perform conversions between number bases and this can also be done with some hand-held calculators. This task can also be carried out using various web resources. (Source: http://en.wikipedia.org/wiki/Web_colors)