Use a diverging color scale when the story depends on both extremes
For extreme-value emphasis in quantitative color-encoded charts, use a diverging color scale on data where both low and high ends matter to improve insight and address one-sided emphasis on only the highest values for readers scanning extremes.
- purpose:refine
- basis:heuristic
- task:extreme
- data:quantitative
- quality:insight
- lever:encoding
- communication:framing
- aesthetic:color:use
advice
Use color to highlight both tails
Use a diverging color scale when the story needs the lowest and highest values to stand out together. For example, replace a sequential light-to-dark map that mainly spotlights the highest values with a diverging map that also brings very low values into focus.
reason
Why diverging scales spotlight both ends
A sequential ramp naturally concentrates attention on its darkest end. A diverging ramp gives visual weight to both tails, so low values no longer disappear into a pale continuation of the same gradient.
Mechanism: Two opposing color directions make both extremes salient instead of giving the strongest emphasis to only one end.
Evidence: The article describes sequential versus diverging as an editorial choice: sequential scales support stories about the highest values, while diverging scales support stories about the lowest and highest values and bring low values into focus (Muth, 2021).
context
Use when both extremes are part of the message
- User Goal: Emphasize both tails of a quantitative distribution.
- Task: Highlight extremes rather than only rank the top end.
- Data: Quantitative values spread across low and high ends.
- Chart Setting: A chart or map already using a quantitative color scale.
- Audience: Readers are scanning for where the extremes are, especially at the low end.
- Success Criterion: Both low and high values are visually noticeable.
exceptions
Do not use when only the high end matters
Break it when: The message is mainly about the highest values. Why: A sequential scale emphasizes that single end more directly.
costs
Costs of emphasizing both tails
Sacrifice: You lose some of the simple one-ended emphasis of a sequential ramp.
Risk: The low end may draw more attention than intended.
Mitigation: Use a sequential scale if the message is only about the high end.
mistakes
Common extreme-emphasis failure
Mistake: Keeping a sequential scale when the intended message is about both low and high extremes. Why it fails: The low end stays visually subdued.
check
Check whether both tails are visible
Failure Sign: Low values blend into the background while high values dominate.
Quick Check: Compare sequential and diverging previews; if only the diverging version makes the low end clearly visible and that matches the story, use it.
Stronger Test: Check whether both tails are easy to spot without reading exact numbers.
fix
Fix one-sided emphasis
- Replace the sequential ramp with a diverging ramp so each extreme gets its own side of the palette.
- Center the diverging scale on the middle point used in the story.
- Revert to a sequential scale if the message is only about the top end.