Parameters are accessed with C4DAtom::GetParameter()/ C4DAtom::SetParameter(). See Parameter IDs.
Parameter: Exponential
COLORMAPPING_EXPONENTIALParameter: HSV Model
COLORMAPPING_HSVParameter: Affect Background
COLORMAPPING_BACKGROUNDParameter: Dark Multiplier
COLORMAPPING_DARKMULTIPLIERParameter: Bright Multiplier
COLORMAPPING_BRIGHTMULTIPLIER