User:Mjpresson/Userboxes/UBX sandbox

These 16 were also specified as sRGB and included in the HTML 3.0 specification which noted "These colors were originally picked as being the standard 16 colors supported with the Windows VGA palette."

X11 color names
In addition, a number of colors are defined by web browsers. A particular browser may not recognize all of these colors, but as of 2005 all modern general-use browsers support the full list. 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 SVG Tiny.

Almost the exact same color names are used in .NET Framework, in the KnownColor and Color enumerations. The only color difference is DarkSeaGreen which is defined as 8F,BC,8B (instead of 8F,BC,8F).

The list of colors actually shipped with the X11 product varies between implementations, and clashes with certain of the HTML names such as green. Furthermore, X11 colors are defined as simple RGB (hence, no particular color), rather than sRGB. This means that the list of colors found in X11 (e.g. in /usr/lib/X11/rgb.txt) should not directly be used to choose colors for the web.

The list of web "X11 colors" from the CSS3 specification, along with their hexadecimal and decimal equivalents, is shown below, compare the alphabetical lists in the W3C standards.

Web-safe colors
Another set of 216 color values is commonly considered to be the "web-safe" color palette, developed at a time when many computer displays were only capable of displaying 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 &times; 6 &times; 6 = 216).

The list of colors is often presented as if it has special properties that render them immune to dithering. In fact, on 256-color displays applications can set a palette of any selection of colors that they choose, dithering the rest. These colors were chosen specifically because they matched the palettes selected by the then leading browser applications. Fortunately, there were not radically different palettes in use in different popular browsers.

"Web-safe" colors had a flaw in that, on systems such as X11 where the palette is shared between applications, smaller color cubes (5x5x5 or 4x4x4) were often allocated by browsers — thus, the "web safe" colors would actually 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.

As of 2007, personal computers typically have at least 16-bit color and usually 24-bit (TrueColor). Even mobile devices have at least 16-bit color, driven by the inclusion of cameras on cellphones. The use of "web-safe" colors has fallen into practical disuse, but persisted in culture.

The web-safe palette system persists as being the palette with the greatest number of distinct colors, where each color can be distinguished individually by human eyes. This led to the use of web-safe colors in anti-phishing systems.

The "web-safe" colors do not all have names, but each can be specified by an RGB triplet. Below are the values for the 6 shades of each color out of 256 possible color shades.

The following table shows all of the "web-safe" colors, underlining the really-safe colors. The lack of gamma correction means that the six desired intensities 0%, 20%, 40%, 60%, 80%, and 100% are displayed as 0%, 2%, 10%, 28%, 57%, and 100% on a Windows standard 2.5 gamma CRT or LCD, making most colors very dark. The intensities at the low end of the range, especially 0 and 3, are nearly indistinguishable from each other:

Color table
Note that in the table below, each color code listed is a short-hand for the RGB value; for example, code 609 is equivalent to RGB code 660099.