Blue Enamel Diamond Cocktail Ring in 18k Yellow Gold. This groovy Mid-Century cocktail ring features .15 carats of single cut diamonds in blue enamel and 18 karat yellow gold. The near colorless diamonds are channel set in yellow gold at the center of the ring. A thick blue enamel coating covers the front of the tapered 18K yellow gold band. This ring is expertly designed and colorful – a timeless work of Mid-Century art!