The effect of particle size on the coloring properties of aluminum dye lakes was studied. Lakes impart color by dispersion in the medium to be colored. Dispersion techniques were developed, using scanning electron micrographs for particle sizing. The color strength and the trichromatic colorimetric properties were calculated from reflectance values measured from "drawdown" films. The results clearly show that the coloring properties of lakes are related to the surface of lake that is wetted by the medium, and resemble results obtained in paint systems. The submicron particles are especially important, contributing greatly to the color strength. The results also agree with theoretical predictions based on certain assumptions for the refractive index of the lakes. The utility of the CIE 1976 L*a*b* color space is demonstrated by quantifying changes in hue, chroma, lightness, and total color difference with different dispersion levels.