I took a typography class in grad school. On the first day, the professor said, “typography is probably the hardest thing in design. Well, second hardest. After color.”

No joke. For instance, these Xs are exactly the same color:

(Look closely at the bottom middle where the Xs meet.)

This sort of thing is what you’re up against whenever you do anything with color.

I’ve written before about how color is a slippery concept, but this article by Nell Greenfieldboyce at NPR does a solid job exploring why that is.

“The agreed-upon technical definition of color,” says Fairchild, “is that it’s a visual perception.”

So don’t try to tell Fairchild an apple is red. He’ll say, no it’s not, technically — red is just your perception.

“I could change the color of illumination on that apple and make it look green or blue or something completely different,” he says. “The redness isn’t a property of the apple. It’s a property of the apple in combination with a particular lighting that’s on it and a particular observer looking at it.”

(Via the Radiolab Tumblr)