Moderate (0.5-1.5 CIELAB units) color differences were scaled and perceptibility ellipses found in different regions of color space. The results are compared with earlier studies and with what the CIELAB formula would predict. Consistency was found between this and several other visual-colorimeter studies; however, there is some disagreement with predictions of the CIELAB equation in the yellow region and with MacAdam data in the blue region. Evidence from this series of papers, of which this study is a part, indicates that there is little or no change in ellipse orientation with the size of color difference, at least up to about 1.5 CIELAB units. -- AATA