The pairing name for the two main characters of the Halo series, the Master Chief and his A.I partner, Cortana. "Green and Blue" is also the name of a track in the Halo 4 Original Soundtrack.
**Spoilers**
The song plays at the end of the Halo 4 Campaign, where the Master Chief is seen in a blue bubble-like hardlight shield, and is confronted by Cortana, only to be told that she cannot accompany him away from The Composer, as the physical remains of her is down at the site of the debris from The Composer.
n. software that is no longer sold or supported by the original publisher / developer, often found as free downloads on the internet because it cannot be obtained elsewhere. Not legal, but often seen as morally acceptable because the company that made it is no longer selling the title, nor releasing it as freeware, therefore abandonware is "keeping the gamealive", so to speak.
Doom II is not abandonware because idstill sells it, while The Incredible Machine is not sold, therefore is abandonware.