wow i love formals. okay best advice i can give you. whatever you wear, do or put on dont forget the best acessory is your smile. laugh and have fun; dont ever forget that.
okay so blue emerald dress hmm i think you have two options here; natural or party. party i would use a black or silver eyeliner preferably silver with some mascar, use wither green, blue or gold eyeshadow, but not too much. for the lips just use some lip gloss you just need a shine.
now with the hair, you say your hair is long? then what you can do is either straighten it till its dead straight, then use a bobby pin and either pin your fringe back into a quiff/puff or pin it to the side. next option is to curl your hair, loose curls and that should look good. hope you liked my advice! have fun, enjoy your day and most imporatntly smile!