Blue light has its own set of virtues and difficulties – the least of which is actually being able to use the tiny window of the misguided term, blue ‘hour’. The dominant hues in the blue hour are actually purples, steely grays and magentas. Also, the ‘hour’ usually lasts for less than half that, and more often than not even less than that.
The key to capturing great blue hour photographs is, more than anything else, knowing what to frame. Unlike the golden light during sunsets, which makes everything look prettier, blue light is not so generous and benevolent. Silhouettes are tricky to capture in blue light without an artificial light source, since not much is discernible against the advancing wall of black in the background. Buildings with their own lighting, such as cityscapes, churches, and factories, are the subjects to concentrate on while shooting in the blue hour. The contrast between the internal lighting and the blue-purple background is the most sought-after setting in blue hour photography.
Landscape shots in the delicate, undulating time between the golden hour and the blue hour are also beautiful. Here, the contrast is provided by natural elements: remnants (or the first signs) of golden light, white clouds, etc. Here’s an example of this technique.