Parameters are accessed with C4DAtom::GetParameter()/ C4DAtom::SetParameter(). See Parameter IDs.
Parameter: GRASS_MAT_PREVIEW
GRASS_MAT_PREVIEW
Parameter: MATERIAL_PAGE_PROPERTIES
MATERIAL_PAGE_PROPERTIES
Parameter: Color
GRASS_COLOR
Parameter: Color Texture
GRASS_COLOR_VAR_SHD
Parameter: Mix Strength
GRASS_INHERITCOL
Parameter: Blade Length
GRASS_LENGTH
Parameter: Blade Width
GRASS_WIDTH
Parameter: Density
GRASS_DENSITY
Parameter: Density Texture
GRASS_DENSITY_SHD
Parameter: Segments
GRASS_SEGMENTS
Parameter: Crinkle
GRASS_STYLE_1
Parameter: Bend
GRASS_STYLE_2
Parameter: Wetness
GRASS_SPECULAR