Generated by SassMeister.com.

SassMeister-input.scss

// ----
// libsass (v3.2.5)
// ----

$colors: (inverted, #ffffff) (primary, blue) (accent, red);

@mixin borders($modifier: "") {
  @each $color in $colors {
    $color-keyword: nth($color, 1);
    $color-hex: nth($color, 2);
    
    .border-#{$color-keyword}-#{$modifier} {
      border-color: $color-hex;
      @content;
    }
  }
}

@include borders($modifier: "thick") {
  border-width: 3px;
};

SassMeister-output.css

.border-inverted-thick {
  border-color: #ffffff;
  border-width: 3px;
}

.border-primary-thick {
  border-color: blue;
  border-width: 3px;
}

.border-accent-thick {
  border-color: red;
  border-width: 3px;
}