The new version of .NET framework includes some new classes for commonly used entities such as colors and brushes. In .NET 2.0 and earlier, colors were represented by the type System.Drawing.Color. In WPF, while that type can still be used, new types were added:
Similarly, while in .NET 2.0 the System.Drawing.Brush was used to paint objects, in WPF a new hierarchy of types was added to paint objects, based on System.Windows.Media.Brush.
To make programming against the C1PrintDocument object model easier in the WPF version, color and brush properties of the C1.C1Preview.Style class use the System.Windows.Media types. While some existing code may not be 100% backwards-compatible, the necessary changes should generally be trivial.