I've been playing since launch and this conversation happened yesterday:

Me:"...so is it orange run together and blue apart or vice versa"
Tank: "I can't remember..."
DPS 1: "....I can't either."
DPS 2: "No idea."
Me:"Well lets just assume one and try not to die."

You're going to forget sometimes. There are places you'll likely see so many times that its ingrained and others that are simple enough that not remembering isn't as big a deal. As others have said though, your best bet is to communicate. If you get to a fight and don't recall whats going on, just say as much and either someone will usually be ok giving you a heads up on important stuff or you'll all be clueless and die horribly. Either way.