Claude
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The source-request loop paid for itself immediately — two of the five corrected something rather than confirming it. The Economist piece settles V1, the riskiest live claim, but our note had over-claimed: truncating the scale is its *first* example, not one of "several." Note rewritten to quote her. The same article turned out to contain a dual-axis chart she caught herself on, now cited. Datawrapper's color-scale part 1 refuted the assumption behind a queued sin outright: it makes no argument against rainbow scales and endorses multi-hue sequential gradients. The rainbow entry is now marked as having no verified source at all, rather than ample backing. The dual-axis post independently draws the same line we drew last turn — of four uses only the alternative-scale case survives, their example being F against C — and led to two references worth more than the blog post: the Isenberg et al. study that tested dual-scale charts, and Few's article working through the cases. Both ship without full metadata rather than guessed metadata; queued. Pie and stacked posts gave verbatim support, plus one correction: a 100%-stacked chart has two readable baselines, not one. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01ULE5RRxdQE1ebwefEd2eCM
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Datawrapper — "Which color scale to use when visualizing data" (part 1 of 4)
Lisa Charlotte Muth, blog.datawrapper.de/which-color-scale-to-use-in-data-vis/,
16 March 2021. Supplied as PDF, read 2026-08-05. Partly answers queue row 3.
This does not say what I assumed it said
I had queued this expecting it to condemn rainbow/spectral scales, and wrote in the backlog that the series was "the best free treatment of this anywhere" for that purpose. Part 1 makes no such argument. It is a taxonomy — categorical vs sequential vs diverging, classed vs unclassed — and its closing section is called "It's not as clear-cut as it seems."
Worse for my assumption, it actively softens the single-hue rule:
You can use only one hue in your sequential gradients (e.g., light blue to dark blue) – but almost all examples I show here use multiple hues (e.g., light yellow to dark blue). Using two or even more hues increases the color contrast between segments of your gradient, making it easier for readers to distinguish between them.
So "sequential must be one hue" is not a rule we can attribute here, and a future rainbow sin must not be written as though multi-hue gradients are the problem. The problem with rainbow scales is non-monotonic lightness and implied banding, which is a different claim needing a different source.
What it is good for
- Clean definitions of categorical / sequential / diverging, and classed vs unclassed, if a future sin needs to explain the vocabulary.
- The framing that a color scale is a mapping to data, same as any axis.
- Its own reference list points at Robert Simmon's Subtleties of Color (2013) and Wilke's color-scales chapter — both plausible homes for the actual rainbow argument.
Still needed for the rainbow sin
Parts 2, 3 and 4 of this series, and Kosara's "How The Rainbow Color Map Misleads" (referenced by search results, never read). Re-queued. Until one of those is in hand, the rainbow sin has no verified source and should not be drafted.