She's a botanist, and she was wearing a feather in her hair, a cerulean blue feather, in honor of the occasion.

WSJ: Of Feathers, Showgirls and Biology

The sky beyond is washed with strokes of cobalt and cerulean blue, and a faint but perceptible smell of aniseed and wild garlic hangs in the air.

BBC: The three colours of Ibiza