The sun had set about 15 mins ago in the north west of Singapore when I captured this photograph from a higher floor of my block of flat. After taking note of the time of the photo, I realised the golden hour had just ended and this was the beginning of the blue hour. The blue hour is the period of twilight, in the evening around the nautical stage for this photo when the Sun is at a significant depth below the horizon. During this time, the remaining sunlight takes on a mostly blue shade. This shade differs from the colour of the sky on a clear day, which is caused by Rayleigh scattering. I dont get to see the sky in this colour in the evenings mostly and it occurs when there was rain in the earlier part of the day or cloudy conditions before sunset. The sky will be pink followed by the onset of blue and finally darkness.