Parameters are accessed with C4DAtom::GetParameter()/ C4DAtom::SetParameter(). See page_maxonapi_getting_started_foundations_cinema_parameters.
Parameter: Color
SLA_BANJ_COLORParameter: Algorithm
SLA_BANJ_ALGORITHMParameter: Illumination
SLA_BANJ_ILLIMINATIONParameter: Roughness
SLA_BANJ_ROUGHNESSParameter: Shadow Intensity
SLA_BANJ_SHADOW_INTENSITYParameter: Clip
SLA_BANJ_CLIPParameter: Contrast
SLA_BANJ_CONTRAST