mdb-ui-kit/scss/mixins/_navs.scss

@mixin mdb-tabs-color($parent, $color, $active-color, $active-border) {
  #{$parent} {
    &.nav-tabs {
      .nav-link {

        color: $color;

        &.active {
          color: $active-color;
          border-color: $active-border;
          @include hover-focus {
            border-color: $active-border;
          }
        }
      }
    }
  }
}