$directions: (
  "top": "t",
  "right": "r",
  "bottom": "b",
  "left": "l",
) !default;

@each $prop, $direction in $directions {
  @each $color, $value in $colors {
    .pp__border-#{$direction}-#{$color} {
      border-#{$prop}: $border-width solid $value !important;
    }
  }
}