Whether you call it cobalt blue or Klein blue, 2026's biggest color trend is absolutely everywhere right now. But for members of the Royal Family, the electric shade has been a favorite for decades.
Princess Kate frequently wears the bright color, as did Queen Elizabeth, who notably remarked that she had to be "seen to be believed." But Princess Diana was perhaps the most fervent cobalt blue fan, wearing the color for everything from her 1981 engagement announcement to glittering evening galas.
