Metamerism is an optical phenomenon whereby two colours appear to be the same when viewed under one source of illumination but not when viewed under another. Two metamers appear different under one source of light but different under another. These colours are called metamers. They might look the same under one type of light, but the way they reflect light is very different. For in... https://www.threenh.com/Color_Knowledge/Metamerism-The-Underlying-Problem-of-Colour-Matching.html