The criteria for a blue -10 is as follows:

Under 48h old.
Never joined a crew.
No record of a wack attempt.
No record of a fort attempt.
No record of a BG wack attempt.

Profiles prior to the wack will show a -1*.

In the obits, you will be able to see if they were blue or red.

(Activities not listed above do not affect the blue status)