The color we “see” on the buildings for that brief second is a visual
phenomenon referred to as a negative afterimage. As the topic of
negative afterimages is very complex, let us simplify the key points to
facilitate comprehension. Our eyes contain
photoreceptors (cones and rods) and “there are 3 types of color
receptors (cones) that are most sensitive to either red, blue or green”
(Washington.edu, n.d).
When you stare at a particular color for too long, these receptors get
“tired” or “fatigued.” In the case of the picture above, the cone cells
in our eyes that respond primarily to the color blue become
overstimulated by the intense blue hue of the first image and
subsequently lose sensitivity. However the cones that respond primarily
to red and green are, more or less, still fresh. So when the picture
switches to black and white, the blue cones can only send out a weak
signal while the red and green cones send out strong signals. The fact
that the color photoreceptors are not in balance results in our seeing
the negative afterimages on the walls of the buildings.