A color specification can contain the name of a CSS SilverLight color, as detailed here:

These color definitions are the same as the Microsoft XAML/SilverLight colors, as detailed here:

Note that the special name "Transparent" from the Microsoft color definitions is supported (though rarely needed).

Alternatively, a color specification can define a color explicitly by prefixing a hexadecimal definition in the form AARRGGBB or RRGGBB with #.

For example, the following will all result in the same color:

{ control: "rectangle", height: "*", width: "*", fill: "CornflowerBlue" }
{ control: "rectangle", height: "*", width: "*", fill: "#FF6495ED" }
{ control: "rectangle", height: "*", width: "*", fill: "#6495ED" }