You can pop out the overlay out to take a look before you even join a raid. The overlay consists of a list of the colors (Blue, Orange, Purple, Yellow) and to the right a name, and a number. The name is one of the people with a shield (which you can use as the next person to take the deletion), the number is how many people have their shield. The overlay does not predict which color or person will be called, it simply shows you a person you can use next for deletion if each respective color is called.