A method for converting source color points of a source color space to target color points of a target color space, said source color space resulting from a combination of N source primary color points and said target color space resulting from a combination of N+1 or more target primary color points in said target color space, wherein N is an integer, the method comprising: for the target color space, defining a set of at least N+1 target primary color points in which color points will be rendered as a combination of said target primary color points; defining an interior color point in the interior of said target color space; dividing said target color space into a set of regions that are bounded by at least two of the N+1 target primary color points and said interior color point; for each said region, calculating a conversion matrix configured to convert N-valued color data belonging to said region in the source color space into N+1-valued color data in the target color space and associating said conversion matrix to said region; for any given source color point in said source color space: determining in which said region the color point lies; selecting the conversion matrix associated with said determined region, using the conversion matrix to convert said source color point into a target color point, wherein said interior color point is an off-white color point of the target color space, characterised in that each conversion matrix, having duplicate rows, is compressed into a smaller dimensioned matrix by removal of duplicate rows of said conversion matrix. for the target color space, defining a set of at least N+1 target primary color points in which color points will be rendered as a combination of said target primary color points; defining an interior color point in the interior of said target color space; dividing said target color space into a set of regions that are bounded by at least two of the N+1 target primary color points and said interior color point; for each said region, calculating a conversion matrix configured to convert N-valued color data belonging to said region in the source color space into N+1-valued color data in the target color space and associating said conversion matrix to said region; for any given source color point in said source color space: determining in which said region the color point lies; selecting the conversion matrix associated with said determined region, using the conversion matrix to convert said source color point into a target color point, wherein said interior color point is an off-white color point of the target color space, characterised in that each conversion matrix, having duplicate rows, is compressed into a smaller dimensioned matrix by removal of duplicate rows of said conversion matrix. determining in which said region the color point lies; selecting the conversion matrix associated with said determined region, using the conversion matrix to convert said source color point into a target color point, wherein said interior color point is an off-white color point of the target color space, characterised in that each conversion matrix, having duplicate rows, is compressed into a smaller dimensioned matrix by removal of duplicate rows of said conversion matrix.