The world is so depressing which is why the sky is usually blue.

They say the sky is the limit because when returning from space you will burn up in the atmosphere.

The sky, the sky beyond the door is blue.

The sky is blue so we know where to stop mowing.

The sky grew darker, painted blue on blue, one stroke at a time, into deeper and deeper shades of night.

When you talk to people about the topics they like talking about they will stick around for more. Talk to them about what you want them to hear and they will soon walk away to return to the grey clouds to talk to the crowd they vowed to converse with.