From Halopedia, the Halo wiki
EB Green is a type of heavy duty tape used by the UNSC. It is extremely resilient, and emerald green in color.
During the Battle of Reach, Frederic-104 used it to secure an M19 SSM Rocket Launcher into the hull of a Banshee flier. The Spartans also use such tape to attach gear such as magazines on their armor.