Many different class names that need similar rules. Easy solution with SCSS.

app.scss

$categories: (
  'somecategory' $yellow,
  'othercategory' $green,
  'thirdcategory' $blue
);

@function category-classes($prefix: '') {
  $classes: ();
  @each $category in $categories {
    $name: nth($category, 1);
    $classes: join($classes, unquote("#{$prefix}.#{$name}"), comma);
  }
  @return $classes;
}


selector {
  #{category-classes('&')} {
    @include single-transition(border-color);
  }
  @each $category in $categories {
    $name: nth($category, 1);
    $color: nth($category, 2);
    &.#{$name} {
      border-color: rgba($color, .6);
      &:hover {
        border-color: rgba($color, 1.0);
      }
    }
  }
}

Thanks to http://portfolio.miphe.com/showcase/sass-dry-selectors/