Eight static grays
Eight static colors: red, blue, green, cyan, magenta, yellow, black, and white
Five dynamic colors: Foreground, Background, TopShadow, BottomShadow, and Select
A transparent "color" that allows the background to show through
These colors are the default colors in Icon Editor. This set of colors provides a reasonable palette with which to create icons. This limited palette was chosen to maximize the attractiveness and readability of icons without using an unnecessary number of colors.
The dynamic colors represent the colors used to display the application on which your icon will appear. If your icon appears in File Manager, File Manager determines what the background color is. Dynamic colors are useful for icons that you want to change color as different color palettes are selected in Style Manager. Dynamic colors are also useful if the icon will be used in more than one place and you want it to use the colors of the application where it appears.
TopShadow and BottomShadow can be used for drawing a shadow under your icon. You can use these colors to make the icon appear to be etched into the surface. This is only recommended for Front Panel style icons.
The transparent color is useful for creating icons that have the illusion of being nonrectangular, since it allows the color behind the icon to show through. If your icon does not fill the entire bounding box, you should fill the unused area with the transparent color.