Web 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.

The first versions of Mosaic and Netscape Navigator used the X11 color names as the basis for their color lists, as both started as X Window System applications. The origin of the X11 color list is unknown. [1]

Hex triplet

A hex triplet is a six-digit, three-byte hexadecimal number used in HTML and CSS, 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. The hex triplet is formed by concatenating three bytes in hexadecimal notation, in the following order:

Byte 1: red value

Byte 2: green value

Byte 3: blue value

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 24, 68 and A0 respectively in hexadecimal notation. To obtain the hex triplet, we simply write the three hex bytes together without spaces, thus: 2468A0. If a byte is less than 16 (decimal) or 10 (hex) it must be represented with a leading zero to keep the number of digits in the triplet equal to six. For example, the decimal triplet 0,1,2 would be represented by the hex triplet 000102.

The number of colors that can be represented by this system is

HTML color names

The HTML 4.01 specification defines sixteen named colors, as follows:

X11 color names

In addition, a number of colors are defined by browsers such as Netscape or Internet Explorer. A particular browser may not recognize all of these colors. Many of these colors are from the list of X11 color names distributed with the X Window System. These colors were standardized by SVG 1.0, and are accepted by SVG Full user agents They are not part of SVT Tiny. They are accepted by most HTML user agents that support CSS, although the CSS WG has chosen not to standardize them for HTML. Some of them, along with their hexadecimal equivalents, are listed below.

Web-safe colors

Another set of 216 color values are commonly considered to be the "web-safe" color palette; developed at a time when many computer displays were only capable of displaying only 256 colors. A set of colors was needed that could be shown without dithering on 256-color displays; the number 216 was chosen partly because computer operating systems customarily reserved sixteen to twenty colors for their own use; it was also selected because it allows exactly six shades each of red, green, and blue. (6 × 6 × 6 = 216). The palette was first identified by Lynda Weinman.

"Web-safe" colors had a flaw that, on systems such as X Windows where the palette is shared between applications, smaller color cubes (5x5x5 or 4x4x4) were often allocated by browsers - thus, the "web safe" colors would dither on such systems. Better results were obtained by providing an image with a larger range of colors and allowing the browser to quantize the color space if needed, rather than suffer the quality loss of a double quantization.

By the early years of the 21st century, driven by the needs of video games and digital photos, personal computers typically had at least 16-bit color and usually 24-bit (truecolor). Even mobile devices has at least 16-bit color, driven by the inclusion of cameras on cellphones. The use of "web-safe" colors fell into disuse, but persisted as folklore.

The "web-safe" colors do not have names, but each can be specified by an RGB triplet. In the table below, a three-digit number is used as a shorthand notation for the six-digit hexadecimal numerals above. The digit "3" is equivalent to the hexadecimal numeral "33"; "C" is equivalent to "CC". For example, "F63" in the table below is equivalent to "#FF6633" in the system used previously. Below are the values for the 6 shades of each color out of 256 possible color shades.

This table shows all of the "web-safe" colors, underlining the really-safe (see next section) colors:

Really web safe colors

Designers were often encouraged to stick to these 216 "web-safe" colors in their websites; however, 8-bit color displays were much more common when the 216-color palette was developed than they are now. David Lehn and Hadley Stern have since discovered that only 22 of the 216 colors in the web-safe palette are reliably displayed without inconsistent remapping on 16-bit computer displays. They called these 22 colors the "really safe" palette; it consists mainly of shades of green and yellow, as can be seen in the table above, where the "really safe" colors are underlined.

CSS Colors

The Cascading Style Sheets language defines the same number of named colors as the HTML 4 spec, namely the 16 listed above. Additionally, CSS 2.1 adds the 'orange' color name to the list:

CSS 2, SVG and CSS 2.1 also allow web authors to use so-called system colors, which are color names whose values are taken from the operating system. This enables web authors to style their content in line with the operating system of the user agent. See [2]. As of early 2004, it appears that the CSS3 color module will once again drop these values, marking them deprecated, but this may change: [3].

See also

• X11 color names
• RGB color space
• hexadecimal
• HTML and CSS
• color
• RGB color model
• alphabetic list of colors, with samples and codes

External links

• Web Color Reference
• Death of the Websafe Color Palette?, an article by David Lehn and Hadley Stern
• VisiBone's "Web-Safe" Color Lab features a more intuitive arrangement of the web-safe colors
• RGB-Color Mixer Applet Java-Plugin required
• Color Table further color tables
• X11 color chart
• HTML Colors
• Introduction to Color Hex Codes More information about color hex codes
• The Color Spot reference information about color definitions in HTML attributes and Cascading Style Sheets
• ColorCombos.com
• THE MOTHER OF ALL HTML COLO(U)R CHARTS — Sites with tables containing large number of colors, including their RGB, CMYK, and HLS values, names, sources, etc.