Optical Illustion: Magic Castle

This is a nice optical illustion,
watch the video, look the center of the image all the time. After a while you will see the castle with some tricks in the colors.

The end of the video tells you the truth, there are no changes in the colors of the castle. When visible clearly, it is just black & while, but the brain does the rest. To check just go backward, without the first part in blue/yellow, you will see is black & while.