I don't get it..

i think is broken

after the bar completes we see black and white photo but it is actully colored photo..

Is an animated GIF so is an image formed by two or more images. Is not an optical ilusion.

Actually your wrong "enter your name " it is an optical illusion that uses the blue color that your eyes see to overload your brain which along with your focusing on one spot for a few moments intensifies the effect. Removing the heavy blue coloring from the black and white image then causes the other normal colors to come into play and fill in momentarily the void left behind before they fade out as your brain reconfigures itself. You can do the same thing with colored lights and you can also get a similar effect by closing your eyes and pointing your face at the sun while your eyes are closed for about 30 - 60 seconds then turn away and open your eyes and everything will have a very blue tint to it.

Ha! Most excellent.