Blue light is known as the wavelength of visible light between the range of 400 and 550 nanometers. The picture below shows the visible range of light for humans and then further breaks out blue light.
Blue light is emitted from the sun, yet at night particles in the atmosphere begin to block some of these "slower moving" wavelengths. That's why sunsets tend to look more orange or red. The picture below shows the irradiance of the sun across the spectrum of colors (wavelengths).
The human eyes picks up on less blue light throughout the day and tells the brain to slow cortisol production (stress hormone associated with wakefulness) and prepares to produce melatonin (the sleep hormone). The picture below shows the daily rhythm of cortisol and melatonin production in relationship to each other.
This is why blue light exposure in your retina can caused delayed melatonin production. Most modern electronics use a white core LED in their displays, which emit high concentrations of the blue wavelength. If you are exposing your eyes to electronics displays before bed, you could be shifting your melatonin production, which will not only affect your sleep that night, but set the precedent for the next night. Our bodies like to maintain the same rhythm everyday. Take a look at the video below to see how the process works.
There are many things that impact your sleep. Blue light is just one factor. To mitigate blue light at night, you can wear blue-blocking glasses 1-2 hours before bed. https://truedark.com/sunglasses/ Also, consider putting dim lights in your room. This is especially important when you wake up during sleep. The best possible solution is to have a Zero-Blue™ light like the one in the Yoga Sleep Node. You can find out more about that here: www.yogasleepnode.com