Naomi Campbell in September 1989 and Halle Berry in September 2010:
Vogue's September issue, the biggest of the year, has a trifold cover with nine supermodels, including three non-white models: Joan Smalls, Imaan Hammam, and Fei Fei Sun. The main cover features Smalls, Cara Delevingne, and Karlie Kloss.
Previously, Vogue's September issue has only featured two women of color: Naomi Campbell in 1989 and Halle Berry in 2012. The 2004 issue was also a trifold with nine supermodels, but included only one non-white model, Liya Kebede, and she was not on the actual cover (only the fold-out pages).
In an article in Vogue's March issue, "Is the Fashion World Finally Embracing Diversity," Sarah Bower suggested that there was a zeitgeist-y crop of non-white models driving the change. She also examined more cynical reasons:
The change is also good for business. The buying power of [Tom] Ford's upper-middle-class African-American clients, he says, is massive. Simultaneously, wealthy markets on the rise in countries like Nigeria, Angola, and Mozambique mean that fashion companies that don't alter their imagery to reflect them will soon be considered strategically inept. The industry has also been quick to find new Asian models in response to the burgeoning Chinese demand for luxury goods.