TREND GAME Champagne Dreams Le Vian paved the way for the popularity of champagne-colored diamonds with its proprietary Chocolate Diamonds, and now the industry is basking in their glow. Engagement rings featuring brown diamonds are sweetly styled and, since brown diamonds typically cost less than their colorless counterparts, tend to be attractively priced. Best of all, the unconventional hue makes the uncommon statement that marriage-minded millennial buyers are seeking.  Top: Sun and Power triangle ring in 14k gold with 0.74 ct. champagne-color diamond, $2,200, Lio and Linn, Brooklyn, N.Y., 646-234-0113, lioandlinn.com; right: ring in 14k gold with 1.95 ct. cushion-cut brown diamond, 0.3 ct. old European–cut diamond, and 0.1 ct. t.w. colorless diamonds, $20,500, Mociun, Brooklyn, N.Y., 718-387-3731, mociun.com; cluster ring in 14k gold with a 0.25 ct. ch