Error compiling bootstrap.scss - Issue with _root.scss

It looks like a bug in SASS compiler itself. Here you have very similar issues:

• https://github.com/twbs/bootstrap/issues/24549

• https://github.com/sass/sass/issues/2383

Try this:

1: :root {
2:   // Custom variable values only support SassScript inside `#{}`.
3:   @each $color, $value in $colors {
4:     --color-#{$color}: #{$value};
5:   }
6: 
7:   @each $color, $value in $theme-colors {
8:     --color-#{$color}: #{$value};
9:   }