This article, in a slightly edited form, first appeared on Pain News Network on  October 26, 2019.

It is a myth that the matador’s red 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.

Color Affects How People Perceive Pain

However, we now know that color also affects how humans 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.

An older study had reported more intense pain when a painful stimulation was preceded by a red color than a blue or any non-color cue. But the current investigation may be only the second study conducted on the effect of color on pain perception.

The authors of the more recent study reported on two experiments. In the first, participants were shown six colors, one at a time, and received 42 electrocutanous stimulations to their forearms – seven shocks with each color. The participants, all of whom freely volunteered to participate in the study and 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 were not necessarily intuitive. Red may bring subjects joy when it takes the form of blooming roses, the shape of succulent berries, or wonderful memories of Christmas celebrations. However, in the study, red still caused a state of arousal that increased subjects’ levels of pain.

The second experiment was designed to assess whether colors would affect expectation of pain and pain intensity. This study’s design was slightly different than the other, but all participants viewed a color and then received a series of electrostimulations. 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.

Coloring Our Perceptions

Our folklore and traditions bestow certain meanings to colors. We all agree that Snow White represents purity and innocence. Edgar Allen Poe uses 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 “Color Hurts: The Effect of Color on Pain Perception” concluded, colors can 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 assessment tools, or even the ambiance of a clinic. Also, 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.” Opinions expressed here are those of the author alone and do not reflect the views or policy of PRA Health Sciences.

You can find him on Twitter: @LynnRWebsterMD.