noun, noun which may take the genitive case particle 'no'
Used as a noun or with の to describe something blue. Common in fashion, design, and everyday color terms.
彼女はブルーのワンピースを着ていた。
She was wearing a blue dress.
空がきれいなブルーだ。
The sky is a beautiful blue.
na-adjective
Colloquial な-adjective meaning feeling sad or depressed, similar to English 'feeling blue'. Often used in casual conversation.
今日はちょっとブルーな気分だ。
I'm feeling a bit down today.
失恋してブルーになっている。
I'm feeling blue after the breakup.