Parameters are accessed with C4DAtom::GetParameter()/ C4DAtom::SetParameter(). See Parameter IDs.
Parameter: Color
FIRESHADER_COLOR
Parameter: U Frequency
FIRESHADER_SCALEX
Parameter: V Frequency
FIRESHADER_SCALEY
Parameter: T Frequency
FIRESHADER_FREQUENCY
Parameter: Turbulence
FIRESHADER_TURBULENCE