Is your green my green? Probably not. What appears as pure green to me will likely look a bit yellowish or blueish to you.

Red, orange, yellow, green, blue, and indigo are all just as real. But purple? Well, purple is just your brain’s way of resolving confusion. That’s right. Red and blue (or violet) wavelengths ...

One reader wonders: Since purple dye was scarce, why didn’t people just combine blue and red? Illustration by Aurélia Fronty Q: I’ve heard that purple was called the royal color because ...