Fringe used to indicate the universe an episode would mostly play in by adapting the title sequence. This way, the different universes were matched with a color, which also makes referring to them in discussion easier.
Not counting the retro-credits for the episodes that played in the past, nor the Observer-infested future of the orange-verse, there are:
- blue-verse: our side, seasons 1 - 3
- red-verse: other side, seasons 1 - 3
- gray-verse: ex-blue-verse that destroyed the red-verse, as seen in "The Day We Died"
- orange-verse: like blue-verse, but Peter died in Reiden Lake, season 4
Was there, however, any color assigned to the other side of season 4 (that would reappear for a few scenes in the finale)? It is not the red-verse, as there are various differences; for example, Broyles died in the red-verse, whereas he is still alive in the other side during season 4.