Board Thread:General Discussion/@comment-15108745-20130811001851/@comment-4010415-20131216083816

Red Trailer - My theory for now is that it's a dream, due to the lines in Red Like Roses and Red Like Roses Part 2, and the fact that the beowolves' blood sprayed out as rose petals ("Every nightmare just discloses / It's your blood that's red like roses").

White Trailer - Quite likely took place in the past. Though, now we're not even sure if the armor fight was a big visual metaphor or if it literally happened.

Black Trailer - Most likely happened in the past, due to the aforementioned evidence of Weiss mentioning the train robbery in Black & White.

Yellow Trailer - Unless the events in the trailer itself occur at some point during the series itself, before Roman gets arrested or dies or whatever's going to happen to him, I think it happened in the past. I wouldn't be surprised if Yang has been hiding her search for whoever the woman in the photo is.