Green is for things I understand, yellow is for “I’m working on it”, and red means I have no clue. I’m mostly using red.
Harry looked around at the stacked shoes and umbrellas remembering how he used to wake every morning looking up at the underside of the staircase, which was more often than not adorned with a spider or two. Those had been the days before he had known anything about his true identity; before he had found out how his parents had died or why such strange things often happened around him. But Harry could still remember the dreams that had dogged him, even in those days: confused dreams involving flashes of green light.
The Borderlands Theme Song