In field biology, describing a lizard as "green" just won't do when the exact shade could be the key to identifying a species. You need to be specific: There's pale green, grass green, citrine, and 48 other greens to choose from in the new Color Catalogue for Field Biologists. Gunther Köhler, who studies reptiles and amphibians at the Senckenberg Museum in Germany, created the book of swatches to standardize color descriptions in science, where reproducible data is a must. The catalog contains 300 hues, as well as patterns, like blotches, specks, and mottling. And while carrying around a pocket guide may seem antiquated, other methods aren't reliable. Preserve a specimen? Nope—ethanol changes its color. Take a picture? Sorry, photos often don't capture true shades. In this case, paper is the best technology for the job.