In the story, the color black and white is represented in many different ways. This picture symbolizes white as knowledge. This can be related to the different impacts light and dark had and the very different connotations they hold.
Raindrops travelling down a window whilst you're sitting inside in the warmth, perfectly dry. Watching the world go by, in the rain. City lights sparkling against all the raindrops that trickle down the windowpane.