But other research suggests that seeing color can be something like tasting foods -- a pleasant flavor for one person may be too bitter or salty for another, just like a single shade of yellow could be seen as pretty or putrid by different people.
In the first phase of the study, the researchers showed that their volunteers (Surrey university students) were slower to notice a target shade of blue when it flashed up against a blue background of adifferent hue than when it flashed up against a green background.
Colors can change shade, or metamerize, under different light sources, so when Harfouch hits on a perfect match he has to be sure it looks the same under sunlight as it does under artificial, supermarket light.