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).
There is a blue bird.
That apple hasn't ripened enough yet, has it?
Wow, this blue paint smells exactly like the red paint.