Not all colors have specific name. Some common colors have name. And how the name will be translated to a hex code depends on the parser. For example, CSS colors are parsed by css parser. HTML colors (bgcolor etc attribute) are parsed by html parser. Desktop environments (e.g. Gnome) also support named color.
You'll find all the color names on Wikipedia article Web Colors. There are HTML Colors, X11 Colors. Most modern web browser supports X11 Colors.
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 of 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 SVG Tiny.