From Halopedia, the Halo wiki
When the Battle for Arcadia occurred in 2531, Cargo 2, alongside Cargo 1 and Cargo 3, was forced to evacuate Pirth City as it fell under attack by the Covenant. The UNSC held off repeated attacks by the Covenant as hundreds of civilians fled to the transports. Despite these attacks, Cargo 2 was able to escape the planet, saving hundreds of lives.
Unlike Cargo 1 and Cargo 3 which are colored blue and white, Cargo 2 is orange and white.
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