Indigo/ˈɪndɪɡəʊ/ Definition 1 of 3Pro Tip 1/2Color Qualifier Indigo refers to a specific shade of blue, darker than sky blue but lighter than navy. She wanted an indigo dress to match the twilight sky. Pro Tip 2/2Color Metaphor Indigo is often used to suggest depth and richness in literature and poetry. His indigo moods were reflective of the stormy seas.