black dress blue dress ZAPAKASA Women and Satin Long Formal with 3D Flowers One Shoulder Mermaid Prom with Ruffles The dress is blue. Here's

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Available Sizes: XS to XXL Advertisement - Continue Reading Below Eloquii's little tiered dress stuns as a wedding guest look

The bright background could be interpreted either as a light source, or as glare (without you even realizing that your brain is making this calculation)

But we understand a lot more about why

"What's happening here is your visual system is looking at this thing, and you're trying to discount the chromatic bias of the daylight axis," Bevil Conway, a neuroscientist who is now a senior investigator at the National Eye Institute and the National Institute of Mental Health, told Wired at the time