There is a blue bird.
That apple hasn't ripened enough yet, has it?
Wow, this blue paint smells exactly like the red paint.
This is a single kanji with an い on the end, meaning you know it's probably an adjective. What's the adjective form of blue? It's still blue! It can also mean unripe, which might sound confusing, but it comes down to the fact that in Japanese there's some overlap between blue and green. So while in English we think of the "go" traffic light and unripe bananas as "green," in Japanese they're actually called "blue."
Since this word consists of a kanji with hiragana attached, you can bet that it will use the kun'yomi reading. You didn't learn that reading with this kanji, so here's a mnemonic to help you:
You have to remember the あお portion to read this word. Think of blue things on your body. Those are bruises. Touch them. What would you say? OW! (あお).