The blue hour is a photographic term. The blue hour arrives shortly before sunrise and after sunset, when the sun's position just below the horizon produces those cooler tones. In contrast to the blue hour is the golden hour. The golden hour occurs just after sunrise and before sunset, when the sun is low on the horizon, creating that signature warm glow. In one article, the author stated that the best time to shoot city night scenes is not really at night but the blue hour. During the blue hour, the city lights are already on and the sky appears dark blue in the pictures which feels like night even it is not dark at all. The biggest advantage is that the sky is still bright which still allow to shoot with your camera hand held at low ISO with which to produce higher quality photos.
The following is a few night photos of downtown Toronto taken during the blue hour with iPhone12 pro max rear main camera.