A colour palette in plain HTML

A template colour palette written as a self-contained HTML file. New palettes can be created easily by copying the file and changing a few CSS variables.

Primary

Hint: Modify as needed by changing the --hue attribute in the inlined CSS.
Usage of a separate color picker tool for this step might be preferable.

Secondary

Hint: You can copy any colour to the clipboard by just clicking on its box. By default colours are copied as HSLA values. This can be changed in the script block at the bottom of the document.

Secondary

Hint: By making use of calc and var, most of the colour palette can be automated. This makes it easier and quicker to make adjustments.