The plot remains largely a mystery at this point other than "a Gothic retelling of Red Riding Hood" (actually it would be 'Little Red Cap' as 'Hood' is the Perrault version) and the IMDB one sentence synopsis:
Set in a medieval village that is haunted by a werewolf, a young girl falls for an orphaned woodcutter, much to her family's displeasure.... but the dress, particularly the one with the horned headdress (which would logically appear to follow the 'walking in blue with boots' one at the head of this post), says a lot. Particularly about transformation, magic, blood magic, lust (and hormones) and innocence.
Until the script and story come to light speculation is king but so far I haven't seen anyone connect the dots like in this particular way. iO9 mentions magic but even the 'sexy superstar' sites haven't twigged to the horned = lust = sexual maturation aspect of Red that I've seen.
Just my take.
Of course, you didn't really think they would do a 'Red' film completely minus the hood, did you? I found the other half to the top photo. Take a look at what Amanda's harried assistant (dresser?) is holding over her arm.
Note: Additional horned headdress costume images via HERE and Amanda-plus-assistant photo found HERE.