By Dr. Lynn Webster, PNN Columnist

It is a myth that the matador’s red cape -- the muleta -- incites rage in the bull and causes him to charge. The truth is, all cattle are colorblind.  The bull does not charge because of the color, but because of the movements of the matador and his cape.

It is not a myth, however, that color can affect the moods of humans. Researchers have studied how colors affect psychological states, such as anxiety, in people.

We now know that color also affects how people perceive pain. In this month’s issue of Pain Medicine, authors Karolina Wiercioch-Kuzianik and Przemyslaw Babel present “Color Hurts: The Effect of Color on Pain Perception,” exploring how color can affect the perception of pain.

A 2007 study reported more intense pain when a painful stimulation was preceded by a red color than a blue one. The new study builds on that work through two experiments.

In the first, 30 volunteers were shown six colors, one at a time, followed by mild electric shocks to their forearms – seven shocks with each color.

The participants, who knew in advance what the research would involve, reported their pain on a scale of 0 to 10 following each stimulation.

A black image was the control to which all the colors were compared. Black was chosen as the control because it is regarded as the absence of color.

The investigators found that the color red produced the most intense pain, followed by green and blue. Other colors were associated with less pain.

The results are not necessarily intuitive. Red may bring people joy when it takes the form of blooming roses, succulent berries, or wonderful memories of Christmas. But in this study, red increased pain levels.

The second experiment was designed to assess whether colors would affect the expectation of pain and pain intensity. Participants viewed a color and then received a series of mild electric shocks. Again, pain intensity was rated higher with some colors, particularly with red, blue and green. The investigators did not observe that specific colors influenced the participants' expectation of pain intensity.

Much has been written about how and why colors can affect our cognition and behavior. Our reactions to colors seem to be a result of biology and cultural imprinting. Interestingly, many people are aware that individuals supposedly have a “personality color.” Human resource professionals have even used color personality tests to assess job applicants.

Our folklore and traditions bestow certain meanings to colors. Snow White represents purity and innocence, while Edgar Allen Poe used a black raven to symbolize death. The Great Gatsby and other stories use the color gold to suggest greed.

Colors affect us psychologically and physically. As the authors of the Pain Medicine study concluded, colors can also influence our perception of pain. Thus, it may be important for researchers and clinicians to recognize that a patient's reported pain could be affected by the colors of the exam room or even the ambiance of a clinic.

It may be time to for people in pain to consider how their choices of clothes, furnishings, and even paint and wallpaper may factor into their levels of comfort.

Lynn R. Webster, MD, is a vice president of scientific affairs for PRA Health Sciences and consults with the pharmaceutical industry. He is author of the award-winning book, “The Painful Truth,” and co-producer of the documentary, “It Hurts Until You Die.”

You can find Lynn on Twitter: @LynnRWebsterMD.

Opinions expressed here are those of the author alone and do not reflect the views or policy of PRA Health Sciences.