Parameters are accessed with C4DAtom::GetParameter()/ C4DAtom::SetParameter(). See Parameter IDs.
Parameter: Source
FIELDLAYER_COLORIZE_SOURCEParameter: Mode
FIELDLAYER_COLORIZE_MODEParameter: Base Color
FIELDLAYER_COLORIZE_COLORBASEParameter: Base Density
FIELDLAYER_COLORIZE_COLORBASE_DENSITYParameter: Top Color
FIELDLAYER_COLORIZE_COLORTOPParameter: Top Density
FIELDLAYER_COLORIZE_COLORTOP_DENSITYParameter: Ink Types
FIELDLAYER_COLORIZE_COLORTOP_MODEParameter: Value as Alpha
FIELDLAYER_COLORIZE_CLIP