Colloidal photonic glasses offer an appealing way to produce vivid colors without any chemical dyes—but so far, a stubborn optical effect has long prevented them from generating a true red color. Now, ...

Add Yahoo as a preferred source to see more of our stories on Google. You perceive electromagnetic radiation in the form of light in all the colors of the rainbow. MirageC/Movement via Getty Images ...

The world is awash with the color purple — lavender flowers, amethyst gemstones, plums, eggplants and purple emperor butterflies. But if you look closely at the visible-light portion of the ...