AbstractThe objectives of this study were two‐fold; to determine how variations in practical illuminance range (from ~300 to ~2300 lx) affect the perception of suprathreshold small color differences for a range of object stimuli across the color space, and to investigate the role of variations in luminance on intra‐ and inter‐observer variability in repeated psychophysical trials. STRESS index and conventional statistical methods suggest the presence of a significant difference between visual responses for large changes in luminance. Inter‐ and intra‐observer variability also varied according to luminance. Calculated color differences based on recent CAM models show good agreement with visual results over the luminance range examined.