also: コバルト・ブルー
noun
A vivid deep blue color, often used in art, design, and fashion.
彼女はコバルトブルーのドレスを着ていた。
She was wearing a cobalt blue dress.
この絵のコバルトブルーがとても鮮やかだ。
The cobalt blue in this painting is very vivid.
From English 'cobalt blue', referring to the pigment made from cobalt compounds.