The pink card in the Kanban board

One of the conventions in Kanban is that when a work item (task) is blocked, a pink (or red) note is usually attached to the task item. Note the reason for obstruction, date.

The blocked work item should be the main focus of the daily station. The impact may become larger after a period of time. You need to let all members of the team know that there is a situation where the blocked issue is escalated and needs to be known to the person concerned.

The team's strong problem management and resolution capabilities are the most basic elements for maintaining work item flows.

--Reading "Kanban method"