From Triad to Qualitative

The process of colorizing a data visualization

In this writing, I discuss how to work with a Triad color harmony to create a Qualitative color scheme. Qualitative color schemes use colors to label different categories of data. There are no implied magnitude differences between each of the categories. This might be a mapping of different routes on a subway, equivalent steps on a flow chart, or types of vegetables in a market are examples of visualizing qualitative data. In building the color scheme, there should be no large variances in lightness or saturation of colors since that can signify importance or preference for a particular category. All colors in the scheme need to be distinctive and distinguishable from one another for both normal color vision and color deficiency individuals.

In general, it is not difficult to build a color theme to support up to four categories that can be considered color blind safe. My previous writing on “Double Complements for a Visualization” highlights an example of a color theme with four different colors that pass color deficiency tests. However, as noted by Joachim Goedhart in his writing on “Data Visualization with Flying Colors”, moving to ranges between five and eight colors becomes extremely challenging. After eight colors, even normal color vision individuals find it difficult to distinguish between…