Diverging Color Scales

A diverging color scale is designed to represent quantitative values that are above and below a certain threshold.

For example, altitude above and below the sea level, comparing the percentage of votes for two candidates etc.

The Desired Properties of a Diverging Color Scale

Technically speaking, the properties are the same as for a quantitative or categorical color scale: uniformity and discriminability.

We use two hues that are easily distinguishable, with the same luminance ramp on both sides (i.e. the change in intensity from the center to one direction must be the same as that from the center to the other direction).

We can create a diverging color scale by combining two individual quantitative color scales that have different hues but the same luminance gradient/steps.

For example, we can combine a quantitative color scale with a red hue with another quantitative color scale that has a blue hue to generate a diverging color scale: