Every chromogenic switchable window gives rise to considerable change of spectral power distribution of the light crossing trough. The filtered light continuously changes during charging/discharging of the device, seen as its coloration/discoloration. As this process occurs continuously, it causes continuous Change of colors on an illuminated multicolored scene. The ability of an electrochromic (EC) switchable unit to modulate daylight and different artificial lights passing through it is studied here. The color rendering properties such a variable light are evaluated. The range of the effect and its consequences on the color of a scene can be adequately described by the change in chroma and hue angle during the modulation of light. These effects were evaluated by different light sources shining through the same EC unit. (C) 2009 Wiley Periodicals, Inc. Col Res Appl, 34. 321-329, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/col.20508