The Red Skulls Illusion: Are Both Skulls the Same Color?

In another episode of "We're going to melt brains this weekend", we have a new optical illusion to present. After the twelve dots, the black and white photos in color, and the boxes that don't move, we come to a pair of skulls. One clearly looks purple, while the other is orange… but there's a problem: We're wrong. Both skulls are the same color. What is going on?

Although we closed last year with the best optical illusions, the truth is that they are never enough. There is always something new to explore, an idea that challenges our eyes and brains. We can't help it. Once our perception and interpretation are challenged in that way, we need to know more. What's next on the list? At first, nothing too strange: Two skulls, one purple and the other orange. However, there is a huge mistake in that description…

These skulls are the same color

Yes, both skulls are the same color. Red, to be more precise. Your eyes and mind scream otherwise, but it is so. If you copy the image into your favorite graphic editor and zoom out, you'll notice the illusion becomes stronger, but when you zoom in (600-800%), the red color is evident. Now, if this illusion seems a bit familiar, it's because we've seen a similar one before. Do you remember the balls of the same color that look red, green, and blue? It's exactly the same: The so-called Munker-White illusion in action.

The explanation is that although we process colors individually, that processing is altered by the tones around the object. In other words, an image "shifts" toward the color of the objects that compose it. The perception of the red skulls changes due to the presence of the vertical blue and yellow bands. Moreover, the blue bands pass in front of one skull and behind the other, with the same effect repeating on the yellow bands.

Source: PopSci