A color space, or model, is a system designed to define colors using numerical values. The red-green-blue, or RGB, color model is used to define colors intended for viewing on display screens for computers and other electronic devices, such as TVs, that use combinations of red, green and blue light to display colors. RGB colors are created by defining the amounts of red, green or blue to combine.
Internet Color Standard
The World Wide Web Consortium, often referred to as W3C, is a group with members from all over the world who work together to develop standards for the Internet. The current W3C-recommended standard for colors is the CSS Color Model, Level 3, 07 June 2011. A CSS, or cascading style sheet, is part of the code that creates a web page that defines colors, format, layout, font and other display properties for page. This standard states that colors can be represented by RGB decimal numbers, hexadecimal numbers or names.
RGB Colors as Decimal Numbers
RGB colors are created by defining the amounts of red, green or blue to combine. In a typical color-picking window, the Custom page may contain options to adjust the RGB values either by typing in a decimal number, using arrows to increase or decrease a value, or by moving a crosshair symbol on a color palette to choose a color. Valid numbers range from 0 to 255 for each color value. For example, to create a medium blue color, use these values:
• Red: 79
• Green: 129
• Blue: 189
To create an orange-gold color, use these values:
• Red: 234
• Green: 177
• Blue: 34
RGB Colors as Hexadecimal Numbers
Hexadecimal, or hex, numbers are six characters long and use a base of 16 rather than a base of 10 that decimal numbers use. Hex numbers are expressed by using numerals 0 through 9 and letters A through F, to represent numerals greater than 9, and these are preceded by a hash mark (#). For example, here are the two colors in the previous section defined in hex numbers:
• Medium blue: #4F81BD
• Orange gold: #EAB122
RGB Colors as Names
In the W3C standard, there is a short list of basic color names such as black, white, red, blue and purple that can be used instead of the numerical RGB value in the CSS code. There is also an extended list of names for specific shades of colors, such as midnight blue, deeppink, and greenyellow, written as one word with no spaces.