The read-only fontFamily property of the CSSFontPaletteValuesRule interface lists the font families the rule can be applied to. The font families must be named families; generic families like courier are not valid.

A string containing a space-separated list of the font families on which the rule can be applied

This example first defines an @import and an @font-palette-values at-rule. Then it reads the @font-palette-values rule and displays its name. As these rules live in the last stylesheet added to the document, the palette will be the second CSSRule returned by the last stylesheet in the document (document.styleSheets[document.styleSheets.length-1].cssRules). So, rules[1] returns a CSSFontPaletteValuesRule object, from which we can access fontFamily.

HTML

<pre id="log">
The @font-palette-values at-rule's applies to the font families:</pre
>

CSS

@import url(https://fonts.googleapis.com/css2?family=Bungee+Spice);

@font-palette-values --Alternate {
  font-family: "Bungee Spice";
  override-colors:
    0 #00ffbb,
    1 #007744;
}

.alternate {
  font-palette: --Alternate;
}

JavaScript

const log = document.getElementById("log");

const rules = document.styleSheets[document.styleSheets.length - 1].cssRules;
const fontPaletteValuesRule = rules[1]; // a CSSFontPaletteValuesRule interface
log.textContent += `${fontPaletteValuesRule.fontFamily}`;

Result

• @font-palette-values at-rule
• font-family descriptor