@mixin test() {
  $values: blue red;

  @each $val in $values {
    color: $val;

    @for $i from 2 through 10 {
      background: $i;
    }
  }

  @for $i from 2 through 10 {
    color: $i;
  }

  @while $k > 0 {
    color: $k;
  }
}