People with anxiety and depression are most likely to use a shade of gray to represent their mental state. Researchers writing in the open access journal BMC Medical Research Methodology describe the development of a color chart, The Manchester Color Wheel, which can be used to study people's preferred pigment in relation to their state of mind.

Peter Whorwell, Professor of Medicine and Gastroenterology at University Hospital South Manchester, worked with a team of researchers from the University of Manchester, UK, to create an instrument that would allow people a choice of colors in response to questions. He said, "Colors are frequently used to describe emotions, such as being 'green with envy' or 'in the blues'. Although there is a large, often anecdotal, literature on color preferences and the relationship of color to mood and emotion, there has been relatively little serious research on the subject."

The researchers created a wheel of colors of various intensities, including shades of gray. They then asked a control group of non-anxious, non-depressed people to describe which color they felt most 'drawn to', which was their favorite and whether any of the colors represented their current mood. When the test was repeated with anxious and depressed people, most chose the same 'drawn to' color as the healthy participants, yellow, and the same favorite color, blue. When asked which color represented their mood, however, most chose gray, unlike the healthy subjects who tended to pick a shade of yellow.

A separate group of healthy volunteers were also asked whether they associated any of the colors with positive or negative moods. According to Whorwell, "When we used these results to separate colours into positive, negative and neutral groups, we found that depressed individuals showed a striking preference for negative colors compared to healthy controls. Anxious individuals gave results intermediate to those observed in depression, with negative colors being chosen more frequently as well as positive colors being chosen less frequently than in the control test."

The Color Wheel provides a unique way of asking patients about their condition that dispenses with the need for language.