1. A method for measuring the efficacy of a stain/tissue combination for histological tissue image data, image data comprising a set of pixels, where the measures of efficacy comprise a statistical measure of clustering performance of the different stain/tissue combinations in the Maxwellian Chromaticity plane, and a representative density of the stain/tissue combinations in the density maps, the method comprising the steps of: capturing of histological tissue image data from a tissue sample that has been stained with at least one stain, the said stain or stains being light absorbent; transforming the histological tissue image data to optical density data, the transformation utilizing the Beer-Lambert law of absorption; projecting the optical density data to the Maxwellian Chromaticity plane resulting in a pure color data representation that is decoupled from the intensity in the transformed image data, wherein the pure primary subtractive colors in the histological tissue image data determine the vertices of the Maxwellian color triangle in the Maxwellian Chromaticity plane, and the projection is a perspective projection and the color data along the achromatic axis project to the Maxwellian color triangle circumcenter; identifying at least one reference color in the pure color data representation in the Maxwellian Chromaticity plane, using a statistical technique; inverting said reference color to form a color mixing matrix with the columns of the matrix being the inverted color reference vector or vectors, the inversion being the inverse of the projection to the Maxwellian Chromaticity plane; deriving a density map, when the mixing matrix is well-conditioned, by applying a pseudo-inverse of the mixing matrix to the optical density data; deriving a density map, when the mixing matrix is medially-conditioned, by applying a piece-wise pseudo-inverse of the mixing matrix to the optical density data; deriving a statistical measure for the clustering performance of the different stain/tissue combinations in the Maxwellian Chromaticity plane; and finding a representative density of the stain/tissue combinations in the density maps.