Simplifying setting colors not in vtkNamedColors.

src/Cxx/GeometricObjects/Cell3DDemonstration.cxx

src/Cxx/GeometricObjects/GeometricObjectsDemo.cxx

src/Cxx/GeometricObjects/Hexahedron.cxx

src/Cxx/GeometricObjects/OrientedArrow.cxx

src/Cxx/GeometricObjects/OrientedCylinder.cxx

src/Cxx/GeometricObjects/ParametricKuenDemo.cxx

src/Cxx/GeometricObjects/ParametricObjects.cxx

src/Cxx/GeometricObjects/ParametricObjectsDemo.cxx

src/Cxx/GeometricObjects/ParametricObjectsDemo2.cxx

src/Cxx/GeometricObjects/ParametricSuperEllipsoidDemo.cxx

src/Cxx/GeometricObjects/ParametricSuperToroidDemo.cxx

src/Cxx/GeometricObjects/Plane.cxx

src/Cxx/GeometricObjects/PolyLine1.cxx

src/Cxx/GeometricObjects/SourceObjectsDemo.cxx

src/Cxx/IO/ImageWriter.cxx

src/Cxx/ImageProcessing/IsoSubsample.cxx

src/Cxx/Images/ImageWarp.cxx

src/Cxx/ImplicitFunctions/ImplicitSphere.cxx

src/Cxx/Medical/MedicalDemo1.cxx

src/Cxx/Medical/MedicalDemo2.cxx