The Power of Color
Connecting your choice of colors and your visualization value
It’s a widely accepted idea that our vision is the most developed, important, and complex of our senses. Not everyone recognizes that fact as based in physiology. Some argue that it may be culturally and historically grounded¹. However, that doesn’t change the fact that humans rely heavily on their vision to explore, analyze, and make sense of the world.
Introduction
One of the main characteristics of a visual object is its color. That’s not accidental; colors can help distinguish between something being in the background versus the foreground, it can contrast differences, bring our attention to an object, and even make us remember objects better.
There’s a subfield of psychology — rather fittingly called color psychology — whose findings are widely used by businesses in marketing and branding. According to Wikipedia:
Color psychology is the study of hues as a determinant of human behavior. Color influences perceptions that are not obvious, such as the taste of food. Colors have qualities that can cause certain emotions in people… How color influences individuals may differ depending on age, gender, and culture… Although color associations can vary contextually between cultures, color preference is relatively uniform across gender and race.
Marketing and branding experts shouldn’t be the only ones concerned with the findings and recommendations of color psychology research; data scientists should also be aware.
Influencing a Mood of Your Audience
Would you rather have your audience excited or bored? Frustrated or calm and friendly? One of the theories of color psychology is that colors can affect our mood. Perception of colors is not uniform; it’s a mode rather than an absolute constant. However, it’s safe to assume that most of your potential audiences would fall into the modal value category.
In 2012, Elliot and Maier² suggested that colors impact our psychological functioning. This theory is known as the color-in-context theory. The central point of this theory is that colors carry meaning and can have a direct impact our cognitive processes, including our attention. The influence a color has is related to our perception of a color being “friendly” or “hostile.” One could expect “hostile” colors to attract attention, while “friendly” colors make us feel safe and sleepy. Red is a prime example of a “hostile” color. That doesn’t mean red brings out negative emotions in people. It means that it attracts attention. In nature, red can have several connotations, among them danger and fear. At the same time, red can signal sexual attractiveness in many species, including humans. Red doesn’t leave us feeling indifferent.
Red is an appropriate color to attract your audience’s attention to the main point of your presentation. A helpful side effect of the emotional impact red has is that an audience will better remember material that’s being presented when red is used to illustrate the data. However, it’s important to remember that moderation is key. If all of your visuals use a red palette, your audience may start to feel agitated and even annoyed. They may remember your presentation, but probably not in a way you want them to remember it.
Color should be used to focus the attention, highlight groups of elements, and to contrast correlations and relationships of data elements.
Making Sense with Colors
In 2008, Castelhano and Henderson³ conducted experiments to determine whether colors could have an effect on how well and how quickly people could gather information about a visual scene. They found that humans made sense of pictures much more quickly if the pictures were in color and if the colors were context-appropriate. In other words, images of objects that are the “right” color are easier for people to understand and make sense of.
This theory is closely related to the idea of semantically resonant colors suggested by Lin et al. ⁴ in 2013. It’s not the first time a close connection between semantics and colors has been shown, but the Stanford researchers helpfully put it into the context of data visualization.
In the United States, most people respond that money is green, love is red, and the ocean is blue. Many concepts evoke related colors — whether due to physical appearance, common metaphors, or cultural conventions. When colors are paired with the concepts that evoke them, we call these “semantically resonant color choices.” — From Harvard Business Review (2014), Sharon Lin and Jeffrey Heer.
Lin and the co-authors found that people perform comparison tasks on bar charts about 10% faster when they’re presented with data in semantically appropriate colors versus randomized color schemes. Below, you can see a pair of bar charts. They each represent fruit sales and are similar to those used in Lin’s experiments. The left one uses a default matplotlib color scheme, while the right one uses semantically resonant colors assigned by their Google Image search algorithm.
Which bar chart is easier to use to answer the question, “are sales higher for apples or tangerines?” What about blueberries versus peaches? The way a semantically resonant color palette is compiled is a fascinating subject in its own right, but it’s not entirely relevant to the topic of this post, so we’ll save it for another day.
The conclusion of Lin’s study was that semantically resonant color palettes contribute to the overall effectiveness of people’s visualization, so it’s crucial to match the content of your data and the colors you choose.
Harmony of Colors
In 2011, Thomas Sanocki and Noah Sulman⁵ conducted an experiment to examine how color matching affects short-term memory (our ability to remember what we just saw).
In the experiment, participants were presented with two sets of color palettes and asked to rate each palette’s harmony. After a short period of time the participants were asked to recall the sets. The sets used in the study were similar to the ones in the image below. The results of this experiment led to the following conclusions:
- People perceive similar color palettes as more harmonious and pleasant.
- Harmonious colors are better retained in our short-term memory than their disharmonious counterparts. “High color-similarity palettes led to significantly higher recollection performance, producing increases in estimated memory capacity, in terms of color units, of 26% to 45%.”
- People remember palettes with combinations of only three or fewer colors better than those with four or more colors.
- The contrast of adjacent colors affects how well a person remembers a color scheme..
The conclusion of Sanocki and Sulman’s study leads to the idea that one can influence an audience’s retention of data by choosing colors that are harmonious and pleasant. However, it’s also essential to maintain a strong contrast between adjacent colors. It’s worth remembering that there are several other types of harmony between the colors, in addition to color harmony based on similarity.
Conclusion
This post only covers a small portion of recent color psychology research. But even this limited review can provide you with useful tools you can use to influence your audience’s attention, understanding, and retention of the information you present. Finally, but still importantly, remember to be aware of the colorblind members of your audience. Both Tableau and matplotlib have color palettes that are suitable for colorblind users. Having additional visualizations in your handout materials that target viewers who have color vision impairments can, at the very least, earn you the gratitude and friendliness of your audience.
References:
[1] Fabian Hutmacher (2019), Why Is There So Much More Research on Vision Than on Any Other Sensory Modality? Frontiers in Psychology, 10, 2246.
[2] Elliot, A. J., and Maier, M. A. (2012), Color-in-context theory. Adv. Exp. Soc. Psychol. 45, 61–125.
[3] Monica S Castelhano, and John M Henderson (2008), The influence of color on the perception of scene gist. J Exp Psychol Hum Percept Perform. 34(3), 660–75.
[4] Sharon Lin, Julie Fortuna, Chinmay Kulkarni, Maureen Stone, Jeffrey Heer (2013), Selecting semantically-resonant colors for data visualization. EuroVis ’13: Proceedings of the 15th Eurographics Conference on Visualization, June 2013, 401–410
[5] Thomas Sanocki, Noah Sulman (2011), Color relations increase the capacity of visual short-term memory. Perception, volume 40, 635–648
