Best Color Palettes for Scientific Figures and Data Visualizations

Choosing the right colors for your data visualizations improves audience comprehension and makes your work accessible to people with color blindness. Color is also an important element of designing scientific graphs and data visualizations because it is a powerful storytelling tool.

Below is a comprehensive guide that will help you create your own effective scientific color palettes and provides resources to help you apply the selected colors in different data visualization platforms. 

What is a Color Palette and Why Should I Care?

How to Find the Best Scientific Color Combinations 

In order to test which colors are best for your scientific project and keep them uniform across platforms, you need to know that every color is defined by different kinds of codes. The main color code that you need to know for scientific publications and presentations are “HEX” codes, which are a six-digit codes that you can use to identify the exact colors that you want to keep consistent across design tools such as Adobe Illustrator, Excel, PowerPoint, Prism, Google Slides, websites platforms, etc. You may also need to know the RGB, HSL, or CMYK color codes for different graphing and data visualization tools. 

To find different color codes, I recommend that you use the tools below:

• Toptal Color Platte Tool - Use this color tool to create, visualize, and download custom, monochrome, analogic, complementary, triad, and quad HEX code color palettes: https://www.toptal.com/designers/colourcode.
• Google Color Picker - Online tool where you can use a color slider to find the HEX, RGB, CMYK, and HSL color codes: https://g.co/kgs/qDGrn3rn3.
• Image Color Picker - Online tool where you can upload an image or provide a website URL and get the RGB Color, HEX Color and HSL Color codes from the image: https://imagecolorpicker.com/en.
• Your Graphing System - Use color formatting tools in your graphing software such as Excel, Prism, R, MATLAB, etc. These tools may not show the color codes, but most will allow you to use an eye dropper tool to select your desired colors from a color palette image.

One incorrect thing I have heard designers say is to “never use red and green together.” They say this because red and green have the most color conflicts for people with color blindness. However, if it is important to your data story, you can use red and green colors together as long as you apply different saturation and lightness to increase the contrast. (See example where high contrasting red and green colors can be used together without a conflict).

Accessible Color Palettes for Charts and Graphs 

The best color palettes for data visualizations are accessible to a wide audience and have clear data storytelling. The examples below provide color combinations and hex codes for a variety of bar charts, line graphs, and pie charts that work well for scientific publications. These examples include hex codes and provide options for sequential, qualitative and divergent color palettes.

Two Color Combinations for Bar Graphs

Three Color Combinations for Bar Graphs

Four Color Combinations for Charts

Six Color Combinations for Charts

Eight Color Combinations for Charts

Data visualization platforms have different options for applying color and using the color codes. Below are resources to help you apply the best colors for graphing platforms such as Adobe Illustrator, Excel, R, Tableau, MATLAB, and Map Generators. 

Color Palettes in Adobe Illustrator

• Color palettes in Adobe Illustrator are called swatches and can be used to make your scientific publications, figures, and posters have professional color consistency.
• The main tool is called the Color Picker where you can enter the exact HEX code or choose any color from the sliders.

Color Palette Tools in Microsoft Excel and PowerPoint

• There are many different versions of Microsoft Excel and PowerPoint, but most of them have an "eye dropper" tool in the color formatting section that allows you to select any color that is available on your screen. This is helpful if you want pull colors from an example image, such as your institution's logo, an example color palette image, or an image with your predefined HEX code colors.
• Some versions of Microsoft will also allow you to directly enter the HEX code in the color formatting settings.
• To find which color tools are available for your version of the software, select the graph, text, or shape element that you want to change using "CRTL + Click" or the Right Click on your mouse and select the color formatting options from the menu options that appear.

Color Palettes in R

• To see a comprehensive list of color palettes available in R, go to Emil Hvvitfeldt's GitHub Resource:
• https://github.com/EmilHvitfeldt/r-color-palettes
• To learn how to apply color in R, I recommend using the open resources available from the University of British Columbia:

https://www.stat.ubc.ca/~jenny/STAT545A/block15_colorMappingBase.html

Colors Palettes in Tableau

• To learn how to apply color to data visualizations in Tableau, visit the Tableau Help Center pages: https://help.tableau.com/current/pro/desktop/en-us/viewparts_marks_markproperties_color.htm

Color Palettes in MATLAB

• MATLab uses RGB values and a color picker code (c = uisetcolor) to define colors.
• Below are two resources that can help you select the right  MATLab color palettes for your graphs and visualizations:

https://www.mathworks.com/help/matlab/ref/uisetcolor.html

http://math.loyola.edu/~loberbro/matlab/html/colorsInMatlab.html 

Colors Palettes for Maps and Cartography

• The best tool for testing color palettes for maps and cartography data is the Color Brewer by Cynthia Brewer, Mark Harrower and The Pennsylvania State University: https://colorbrewer2.org/#type=sequential&scheme=BuGn&n=3

Color Palettes for Scientific Poster Backgrounds

• Use this resource article to learn more about good research poster design: https://www.simplifiedsciencepublishing.com/resources/free-research-poster-templates-and-tutorials

Tool to Translate a Color into Any Format

• Use this Color Hex tool to find all of the color codes from a HEX color code such as RGB, HSL, CMYK, and many others: https://www.rapidtables.com/convert/color/index.html.
• This may be helpful if you need to translate your desired colors to a software or graphing platform that uses a less common color code.

How to Use Color to Tell your Scientific Story

The goal of selecting colors for your data visualization is to help your audience quickly understand the main point of the information. One effective method to improve color design for data visualizations is to only apply color to the elements that you want to attract your audience's attention. 

For example, the graphs below both use the same data, but the graph on the right changes the order, improves formatting, and selectively uses color to draw your eye to the most important information. After you create any data visualization, you should ask yourself whether the colors highlight the main point of your scientific story, and if not, consider revising your color design.

Read these articles to learn more scientific story design tips and tricks:

• Scientific Data Visualization Tools and Techniques
• Data Storytelling: How to Tell a Great Data Story in 4 Steps

Grayscale is a Good Default Option

Although color can be used as an effective tool to tell your data story, it is also important to note that grayscale colors are still a great way to represent your data. The key to using grayscale in scientific research is to make sure that there is approximately a 15-30% difference in saturation between the colors used (e.g. shades of gray). Most default color guides are already set up to help you select gray colors that are not too similar.   

References:

• Statistic of number of people with CVD from https://www.colourblindawareness.org/colour-blindness/