A color scale, also called a color ramp or continuous palette, assigns colors along a smooth progression so continuous values communicate both order and magnitude. section 4.3.1
Use these design guidelines when building a scale:
- Start with one hue, then vary lightness or saturation so larger values visibly carry more color. section 4.3.1
- Vary lightness as well as saturation to preserve distinctions in black and white and improve color-vision accessibility. section 4.3.1
- Consider two hues when a single-hue gradient lets low values disappear into the background or fails to provide enough contrast. section 4.3.1
- Choose a diverging scale when both low and high extremes deserve emphasis rather than only the larger values. section 4.3.1
A single-hue sequential scale
A scale can hold hue at 270 degrees in HSL space while moving saturation from 0% to 100% and lightness from 100% to 50%, creating a progression from white to full color.
Figure 4.22 A continuous sequential color palette, made in HSL space by selecting hue = 270, varying the saturation from 0% (no color) to 100% (full color), and varying the lightness from 100% (white) to 50% (full color).
Inspect how a continuous sequential palette changes as saturation and lightness vary across HSL space. section 4.3.1
