Ray-Ban has added a fluid coloring for the lenses and frames of its Wayfarer eyewear, called Iridescence. It's not an optical illusion. The lenses are made of silica micro-crystals that are coated with refractive metal oxides. Depending on the power and angle of light, the oxides produce various colors that blend with one another, producing a liquid appearance. The frames undergo the same treatment and respond to sunlight similarly. Read more.