A mural of Personality Cores floating on a rainbow and the Rainbow Core can be seen in a secret room in the first test which is related to the achievement Single Rainbow.
After the interaction with the Rainbow Core, Virgil stutters and asks if Mel got the core's serial number. This has led fans to believe that Virgil is implied to be homosexual as he shows attraction to a male personality core.
Rainbow Core’s voice actor, Harry Callaghan, voices all of game characters except Virgil (he's voiced by Stig Finsen Sydtnagen). He is also the creator of the popular Portal fan series, Meet the Cores which planned to feature Rainbow Core in it's third installment, and was mentioned in the second one.
The track during this chamber is called Testing with Nature.
