Date Published: April 17, 2019
Publisher: Public Library of Science
Author(s): Tarja Peromaa, Maria Olkkonen, Daniel Osorio.
The color red seems to be consistently associated with the concept of anger. Beyond semantic associations, it has been suggested that the color red enhances our ability to perceive anger in faces. However, previous studies often lack proper color control or the results are confounded by the presence of several emotions. Moreover, the magnitude of the (potential) effect of red has not been quantified. To address these caveats, we quantified the effect of facial color and background color on anger with psychometric functions measured with the method-of-constant-stimuli while facial hue or surround hue was varied in CIELAB color space. Stimulus sequences were generated by morphing between neutral and angry faces. For the facial color, the average chromaticity of the faces was shifted by ΔE 12/20 in red, yellow, green and blue directions. For the background color, the hue was either neutral or saturated red, green or blue. Both facial redness and surround redness enhanced perceived anger slightly, by 3–4 morph-%. Other colors did not affect perceived anger. As the magnitude of the enhancement is generally small and the effect is robust only in a small subset of the participants, we question the practical significance of red in anger recognition.
We intuitively associate red with danger, anger, and arousal . These associations seem to be consistent across cultures  as well as across species, as illustrated by the warning and socio-sexual displays of many animals (e.g. [3, 4, 5, 6]). Even the evolution of language points to a role of red as an important signal color: red is consistently the first chromatic color category to emerge after a light/dark or warm/cool split [7, 8, 9].
We studied the effect of facial and background color on the perception of anger by characterizing anger detection thresholds in color-calibrated stimulus displays. Red facial and background color enhanced the perception of anger by 3–4 morph%, while yellowish, greenish or bluish facial or background color did not have an effect on thresholds. This effect was significant but relatively small and robust only for a minority of the participants. We discuss the results for facial and background color separately first, and then compare the two. Finally, we assess the practical significance of the effect.