Each of the 40 self-adhering metamerism stickers is finished with 2 different colors that integrate seamlessly with each other. For the correct D65 light source with CIE spectrum, both color fields appear almost identical (a minimal difference is apparent due to pigmentation).
If the light source substantially deviates from the standard D65 illuminant in spectrum or color temperature, both fields will reflect the incoming light differently and you will see 2 colors.
Adhering Lighting Indicator to products and press proofs allows everyone involved in the process to immediately determine which lighting is correct for making the color comparison.
Term definition:
Metamerism or metameric colors refer to color pairs that look identical when a defined illuminant is used and appear differently when another illuminant is used.
Example: Illuminant D65 in standardized lighting booths (correct; color fields look almost identical) and a TL84 fluorescent tube on the office ceiling (incorrect; color fields look very different) as depicted in the photos. Doesn't react on continuous spectrum as lgiht bulbs with light source A or LED.