Based on my LinkedIn feed, color is the one topic in data viz we just can’t stop talking about. Coming from a fashion design background, the idea that color needs intention is very familiar. In a fashion collection, designers use color, silhouette, and texture to guide attention and tell a specific story. While ten designers might tell ten different stories, every design choice is intentional and follows the same structural rules.
In data viz, those rules generally fall into three main categories:
1. Encoding: Representing a range of data
This is where color actually holds the data. A heatmap is the best example: the intensity of the color represents the height of a value. Without it, the map would be literally empty. To do this effectively, different gradients are used. Sequential palettes focus attention on one end of a range, while diverging palettes emphasize both opposing ends. By using a neutral mid-value, "normal" values are de-emphasized to let the extremes stand out. The charts below show the exact same data, but the different palettes highlight completely different stories.
2. Distinguishing: Representing categories
Color can also separate groups like regions or departments. Unlike gradients, this requires categorical palettes where each color is distinct yet carries equal weight. To avoid accidentally implying a hierarchy, these colors should have similar brightness and saturation. The goal is enough contrast to tell groups apart at a glance, creating variety rather than a rank.
3. Emphasis: Highlighting the story
Color is the fastest way to show exactly where to look. By using a single "Action Color" against a neutral background, the most important data stands out immediately. To make this work, the rest of the chart should stay in a muted grey or a transparent version of the highlight color. This keeps the focus on the takeaway without the rest of the data feeling disconnected.
There is much more to consider, such as accessibility or brand identity. But mastering these three foundations provides a solid basis for using color with purpose. When these are in place, color stops being decorative and becomes a deliberate design choice.