![255 255 255 1 255 255 255 1](https://www.baslerweb.com/fp-1485687431/media/editorial/content_images/faqs/faq_RGB_1.gif)
A (alpha) can be a between 0 and 1, or a, where the number 1 corresponds to 100% (full opacity). R (red), G (green), and B (blue) can be either s or s, where the number 255 corresponds to 100%. For example, #0f38 is the same color as #00ff3388. Likewise, the four-digit RGB notation ( #RGBA) is a shorter version of the eight-digit form ( #RRGGBBAA). For example, #f09 is the same color as #ff0099.
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The three-digit notation ( #RGB) is a shorter version of the six-digit form ( #RRGGBB). R (red), G (green), B (blue), and A (alpha) are hexadecimal characters (0–9, A–F). For example, #ff0000 is equivalent to #ff0000ff. In browsers that implement the Level 4 standard, they accept the same parameters and behave the same way. Note: As of CSS Colors Level 4, rgba() is an alias for rgb(). CSS Colors Level 4 added the rebeccapurple keyword to honor web pioneer Eric Meyer.
![255 255 255 1 255 255 255 1](https://echip.vietnamnetjsc.vn/2013/04/06/07/45/Network00402.png)
They are called the extended color keywords, the X11 colors, or the SVG colors. Although various colors not in the specification (mostly adapted from the X11 colors list) were supported by early browsers, it wasn't until SVG 1.0 and CSS Colors Level 3 that they were formally defined.CSS Level 1 only included 16 basic colors, called the VGA colors as they were taken from the set of displayable colors on VGA graphics cards.Note: The list of accepted keywords has undergone many changes during the evolution of CSS: Though many keywords have been adapted from X11, their RGB values may differ from the corresponding color on X11 systems since manufacturers sometimes tailor X11 colors to their specific hardware.Several keywords are aliases for each other:.The color keywords all represent plain, solid colors, without transparency.Unlike HTML, CSS will completely ignore unknown keywords.The other color keywords should only be used in CSS and SVG. HTML only recognizes the 16 basic color keywords found in CSS1, using a specific algorithm to convert unrecognized values (often to completely different colors).There are a few caveats to consider when using color keywords: Although the names more or less describes their respective colors, they are essentially artificial, without a strict rationale behind the names used. Color keywords are case-insensitive identifiers that represent a specific color, such as red, blue, black, or lightseagreen.