In response to a question on Twitter by @everybody_kurts:
“Hi @mbostock, I was looking at your stacked area chart at https://observablehq.com/@d3/stacked-area-chart. At the end of the file, you import swatches from “@d3/color-legend”. I tried finding this on npmjs but to no avail. Is this exclusive to @observablehq only?”
This shows how to use the swatches function from the @d3/color-legend notebook in a plain HTML page. The example data for the swatches (the color scale and margin) is copied from the @d3/stacked-area-chart notebook.