I never really thought about the meaning of the Frontex logo before, so if you do not know, here is the answer from the Frontex web site:
“What is the meaning of Frontex logo?
The logo represents land border (green line), sea border (blue circle) and air border (background) linked by EU stars. There is also the self-explanatory inscription: Libertas, Securitas, Justitia.”
MIGRANTS AT SEA 