The Subway icon set is a group of CSS only icons. The color of the icon is set with the background color utility `bg-` with a name that follows the [primary trunk line nomenclature](https://en.wikipedia.org/wiki/New_York_City_Subway#Nomenclature), ex: `bg-<trunk>`.

    <span class="icon-subway bg-lexington-avenue">6</span>

For express stops, the border color utility `border-<trunk>` is set instead of the background.

    <span class="icon-subway icon-subway-express border-lexington-avenue">6<span>