"My new dress is red."
Translation:Ma nouvelle robe est rouge.
The slang word I know for a "certain" male body part is feminine. Go figure!
My favourite sentence in french is, "Le problème est toujour masculin, mais la solution est toujour féminin." (The problem is always masculine, but the solution is always feminine. Just a little fun with masculine/feminine nouns.)
Nouvelle goes before robe because it quantifies the Age of the dress.
See this for more details about the B.A.G.S. pneumonic: http://french.about.com/od/grammar/a/adjectives_4.htm