Fame Pictures

It wasn't exactly a dress rehearsal, but Kate Middleton demonstrated her dark taste in wedding fashions when she stepped out Jan. 8 to attend friends' nuptials with Prince William and some of her future in-laws.

The princess-to-be grabbed headlines in the United Kingdom for wearing (gasp!) a nontraditional black velvet Libélula jacket and fluid above-the-knee black dress with sheer neckline to attend the late-afternoon Yorkshire ceremony of royal buddies Harry Aubrey-Fletcher and (Louise) Sarah Stourton.

Prince William was reportedly an usher for longtime friend Aubrey-Fletcher. The ceremony was also attended by Middleton's future brother-in-law, Prince Harry, and a royal-blue-clad Princess Beatrice, daughter of Prince Andrew and Sarah, Duchess of York.

In royal eras past, black has been avoided for everything but funerals. The late Princess Diana made waves in 1981 when she appeared at one of her first official appearances with then-fiancé Prince Charles wearing a sexy floor-length black dress with plunging neckline by her wedding dress designers, David and Elizabeth Emanuel.

Middleton's perfectly polished guest look included a diminutive black pillbox hat, sheer stockings, plum-violet pumps with bow details and coordinating slim violet clutch.

Two U.K. news outlets, the Daily Mail and All Voices sniped that Middleton was looking gaunt and pounced on her color palette. "Black? For a wedding? Slim Kate's unusual choice," was the Daily Mail's front-page headline. The paper also urged her to eat a few "hearty meals' before her own April 29 wedding.

Yet Middleton's choice of her elegant Libélula topcoat was another nod by the future royal to an up-and-coming British designer. The brand, distinguished by its bright, fluid frocks and floaty colorful blouses, was established in 2002 by Sophie Cranston, 1999 winner of the U.K.'s prestigious Designer of the Year Award at London's Graduate Fashion Week. The award has previously been bestowed on such megawatt fashion names as John Galliano, the late Alexander McQueen and Burberry's Christopher Bailey.
.
Cranston was reportedly mentored by another Middleton fave, Alice Temperley, whose pretty cream-and-black embellished dress was her pick to wear to a charity function last month with Prince William.

Middleton caused a sensation when she stepped out in a royal-blue dress by Issa designer Daniella Issa Helayel to announce the royal engagement in November and another retail phenomenon when she wore a mid-priced cream-colored dress by Reiss in her official Mario Testino engagement photos. Middleton also wore a blue dress by Issa and a black jacket when she and the prince were guests at the fall 2010 wedding of Harry Meade.

Meanwhile, read about the sheer dress Middleton wore long ago that's become a valuable royal artifact.

And find out the 8 royal rules of style (Kate already broke 2 of them with this look!).

Read the latest on Middleton and Prince William's elaborate wedding plans at www.royalwedding.aol.com