Creating an entirely neutral base and then "popping" only one item of color is an easy way to achieve a more slender silhouette. Underneath the jacket I'm all black and grey with a sophisticated lace top, grey pencil skirt, opaque black tights and black boots. This creates a long lean solid line. Topping it all off with the rich rust leather jacket and faux leopard bag creates a more casual look.  This jacket could have been any other color in the rainbow and the entire outfit would have still worked brilliantly due to the neutral base.

top – H & M
skirt – Ricki's
shoes & bag – TJ Maxx
Jacket – Danier
necklace – Le Chateau