IDocs are assigned to a Status Group, depending on their processing status (e.g. status group 2 = Outbound: IDoc ready for dispatch).
In the IDoc Display, these status groups are divided into 3 categories ( successful, error or not yet processed), represented by green, red and yellow traffic lights respectively. You can change the assignment of status groups to traffic light colors in the Edit Status Groups transaction.
The traffic light color green (code 2) is assigned to the status group 3 ( Outbound: IDoc in external system). You want to change the traffic light code for this status group to 1 (yellow).