The IfcIndexedColourMap provides the assignment of colour information to individual faces. It is used for colouring faces of tessellated face sets.

• The IfcIndexedColourMap defines an index into an indexed list of colour information.
• The Colours are a two-dimensional list of colours provided by three RGB values.
• The ColourIndex attribute corresponds to the CoordIndex of the IfcTessellatedFaceSet defining the corresponding index list of faces.
• The Opacity attribute provides the alpha channel for all faces of the tessellated face set. The next image shows an indexed colour map.

Indexed colour map geometry: 

On this image IfcTriangulatedFaceSet is represented by:

• IfcTriangulatedFaceSet.CoordIndex: ((1,6,5),(1,2,6), (6,2,7), (7,2,3), (7,8,6), (6,8,5), (5,8,1), (1,8,4), (4,2,1), (2,4,3), (4,8,7), (7,3,4))
• IfcCartesianPointList.CoordList: ((0.,0.,0.), (1.,0.,0.), (1.,1.,0.), (0.,1.,0.), (0.,0.,2.), (1.,0.,2.), (1.,1.,2.), (0.,1.,2.))
• IfcIndexedColourMap.ColourIndex: (1, 1, 2, 2, 3, 3, 1, 1, 1, 1, 1, 1, )
• IfcColourRgbList.ColourList: ((1.,0.,0.), (0.,1.,0.), (1.,1.,0.))

changes 

• IFC4X3_RC1 changes: Type of the ColourIndex attribute changed from INTEGER to IfcPositiveInteger.