Related Questions:
Different colored arrows in my Booking Pipeline
Colored arrows in my Bookings list
Task Colours
Colours on my booking
Environment:
Event Temple Web App
Answer:
The arrows on the right side of your Bookings in your pipeline and list view represent that state of the Tasks on that Booking.
Black/Blue: No tasks currently assigned to that booking
Green: Tasks assigned, but none due/overdue
Yellow: Tasks assigned and one or more is due today
Red: Tasks assigned and one or more is overdue