It's possible to create different lists in Trello, with different name, colors, etc. Some of them are based on the Kanban methodology. However, there are a lot of lists that are not created using Kanban. Kanban WIP for Trello allows you to create lists with work-in-progress limits and limits for cards with specific labels (green, yellow, red, blue, sky, lime, pink).

These limits are used to manage the work done by the people in a team. With this extension, it's easy to set a work-in-progress limit of 5 cards to the list and also add exclusions to the list.