Understanding the Black and Blue Dress Illusion Ten years ago, a photo of a dress posted on Tumblr sparked a massive debate: was it blue and black or white and gold? Millions argued online, and even celebrities joined in. Scientists later explained This explains how the blue black white gold dress illusion was possible. But it doesn't explain why some people saw it one way and some saw it the other, and no one seemed to see Here's why people saw the dress differently.