"Roy G. Biv" was an alias used by the primary antagonist of season 1.
Sam and Max first encountered the name "Roy G. Biv" during Reality 2.0 when visiting bancolavadero.com to transfer money to Bosco's account. They both figured the name was a pseudonym and moved on. In the end, the Internet revealed that she had been manipulated by someone using that name, but crashed before she could tell Sam and Max who Biv actually was. In the following episode, Sam figured out who it was: Hugh Bliss, founder of Prismatology.
The name "Roy G. Biv" is actually an acronym for the colors of the rainbow: Red, Orange, Yellow, Green, Blue, Indigo, Violet, which fits with Hughs' love of colours.