1. A method for converting an externally defined four dimensional colorant into an equivalent four dimensional colorant having color components of a given printer, the method comprising: measuring first color values of a first set of patches having predetermined combinations of varying percentages of three primary colors (known ABC values) printed by the given printer; correlating each combination of known ABC values with the corresponding color values as input to a first inversion program for determining ABC values for any given color values; measuring second color values of a second set of patches having predetermined varying percentages of a fourth colorant (D) printed by the given printer; using the first inversion program to determine ABC values corresponding to the color values for the varying percentages of the fourth colorant; using the determined ABC values corresponding to the second set of patches and the known ABC values of the first set of patches to determine an equivalent fourth colorant substitution for the first patches having new ABC values (A'B'C') and a corresponding percentage of the fourth colorant (D); and correlating each combination of A'B'C' and D with associated color values as input to a second inversion program for determining A'B'C' and D values for any given color values or equivalent values.