Departures from exact ellipticity when color‐discrimination ellipsoids or ellipses are translated to CIELAB have been numerically analyzed. The greatest distortions for ellipses were around 5% at the most saturated orange‐red centers. The distortions for ellipsoids were of the same order as those of the ellipses at the five CIE centers. These small distortions are well covered by the interobserver variability and could be ignored in most cases, but an appropriate method must be used for the translation of color‐threshold results to CIELAB. Experimental results published by Luo and Rigg for 132 chromaticity‐discrimination ellipses are expressed in CIELAB. These results may be useful in checking the performance of new color‐difference