Parameters are accessed with C4DAtom::GetParameter()/ C4DAtom::SetParameter(). See Parameter IDs.
Parameter: Color
VP_COMICCOLORParameter: Illumination
VP_COMICILLUMINATIONParameter: Outline
VP_COMICOUTLINEParameter: Edges
VP_COMICEDGESParameter: Edge Color
VP_COMICEDGECOLORParameter: Background Color
VP_COMICBACKCOLORParameter: Quantize
VP_COMICQUANTIZEParameter: Steps
VP_COMICQUANTIZELEVEL