Color communicates a visual message by setting tone, creating emotional connection, directing attention, and linking data with the audience. Hue identifies the color family, saturation describes intensity, and brightness indicates lightness or darkness. section 8.2
Choose a palette according to the relationship the chart needs to show:
- Use a sequential palette when quantitative values progress from high to low through gradients or saturation changes. section 8.2
- Use a diverging palette when contrasting extremes and a lighter middle must show a spectrum such as cold to hot. section 8.2
- Use a qualitative palette when separate hues distinguish categories rather than numerical magnitude. section 8.2
- Assign a primary color to the main character, an alternative color to its adversary, and gray when pushing the adversary into the background. section 8.2
Changing the message with color
A population chart originally uses green for North America's trend. Changing the main chart to dark red (#963232) gives slower growth a more negative emphasis, while retaining green for the optimistic strategy chart preserves a constructive contrast. Set colors locally when one layered chart should remain unaffected by global configuration. section 8.2.2
Creating a negative visual context
A salmon chart emphasizing negative years combines a shocking disease image, dark red (#460805), and a thicker line over 1992–1998. The focused overlay uses transform_filter() to isolate the selected category and years. section 8.7.1
Figure 8.2 A sequential color palette
Compare the sequential, diverging, and qualitative palette figures to match palette structure with the intended data relationship. section 8.2
