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Check chart series colours for contrast, colour-blind confusion and too many hues against your background

Chart colour checkFreeFor designers and developers

25/day

free runs a day, no sign-in.

Before: what you give it

The example input, as typed in. You paste text, CSS, markup or notes.

colors: ["#d55e00","#009e73","#56b4e9","#f0e442","#cc79a7"]
background: #ffffff
chartType: line

After: what comes back

The first lines of a real run on that input. Nothing here is edited by hand.

Colour check: 5 colours on #ffffff, line
3 errors.

[ERROR] Colour 3 (#56b4e9) has 2.31:1 against the background #ffffff; graphics need 3:1. The closest passing shade is #229de2.
[ERROR] Colour 4 (#f0e442) has 1.32:1 against the background #ffffff; graphics need 3:1. The closest passing shade is #a1970d.
[ERROR] 4 pairs too close in greyscale (print or low-vision settings). Worst: colours 1 (#d55e00) and 2 (#009e73), difference 4 where 15 is the working minimum for thin marks.
[WARN] 5 series. Past four, a legend forces readers to match colours by memory. Label each line at its right-hand end, and add a second cue (dash style, marker shape, or position) so colour is not the only carrier.

Wong palette colours holding 3:1 on this background: #000000 #009E73 #0072B2 #D55E00 #CC79A7

What you get

Contrast per colour with nearest passing shade, confusable pairs under four vision models, Wong palette fit

What it cannot do

Takes up to 24 colours; the delta E cut-offs of 10 and 15 are working conventions, not standards.

Who it is for

  • Designers
  • Developers

Free and Pro

Free25 runs a day per IP address.
ProNo daily limit, 300 requests a minute.

What each plan includes

Use it from your assistant

The tool is called chart_colour_check. Connect the server once, then ask for it by name or just describe the job. Install steps for each app.

claude mcp add --transport http designers https://designers.allthepossibles.com/mcp
curl -X POST https://designers.allthepossibles.com/api/chart-colour-check -H 'content-type: application/json' -d '{"colors":["#d55e00","#009e73","#56b4e9","#f0e442","#cc79a7"],"background":"#ffffff","chartType":"line"}'

Try it here

The form starts with the same example input, so you can run it first and then swap in your own.

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