It's not an optical illusion—the glass inside the creative agency Canvas Worldwide's new Los Angeles office does change throughout the day. Like a visual mood ring, the iridescent expanse changes its gradient sheen depending on the time of day and the angle you see the glass. If Rainbow Brite were an account exec, she'd request this for her office.
This visual effect is thanks to dichroic glass, a material that interrupts light waves. The physical effect is called "thin-film interference," which is why soap bubbles and oily puddles sometimes have a rainbow sheen. Light hits one side of the film and is reflected at a different angle, changing the color our eyes see. 3M produced the glass finishes that created this brilliant rainbow effect.