switch from screen to printing books - for better sleep. Why?
Screen of computer/cell phone, emits blue light, disrupting the release of melatonin, hormone promoting sleep.
Don't lie down on bed, reading your cell phone or iPad - bad habit! The closer to your eyes, the more exposure to blue light you got, the worse effect on your asleep.
Don't use "blue color" as blue is color, redundant. You can say blue light, blue flag, blue cloth.