You raise a Purchase Order and the workflow is set or can be chosen.
Typically an approver gets an email and asks to approve or reject
They are taken to a web page and have two options - Approve or Reject
If they approve, the next step of the workflow will trigger - perhaps another approver email or the email to the supplier.
In this scenario, the dashboard light will be green.
If they reject the Purchase Order it will be Red
The dashboard light will be Orange whilst the process is incomplete