RiRi pulled out all the stops at December’s first annual Diamond Ball, starting with a super-glamorous off-the-shoulder Zac Posen gown. She played up the rich russet hue with dark cherry lips, and carats upon carats of Chopard rubellite, rubies, and diamonds. Meanwhile, for the Billboard Women in Music luncheon, Beyonce? called on her go-to jeweler, Lorraine Schwartz, for some daytime-appropriate bling. Turns out trendy yellow gold is a particularly great accent for 2015’s Color of the Year. Of course Queen Bey knew that.  Rihanna’s OriginalRed Carpet collection ring with a 49.64 ct. rubellite, 3.2 cts. t.w. rubies, and 1.27 cts. t.w. diamonds in 18k white gold; price on request; Chopard, NYC; 800-CHOPARD; chopard.com Under $20,000Ring with 10.08 ct. oval pink tourmaline, 1.1 cts. t.w. pear-shape rubies, and 0.56 ct. t.w. diamonds in 18k rose gold; $18,500; Omi