Using CSS Variables as Sass function arguments

Is there a way to use CSS variables with Sass functions e.g. lighten? Something like this:

:root {
  --color: #ff00ff;
}

.div {
  background-color: lighten(var(--color), 32%);
}

I'm getting an error message that "Argument $color of lighten($color, $amount) must be a color".

I'm using CSS (not Sass) variables, because I need to use them in js.