Blue–green distinction in language describe certain vegetables, apples, and vegetation. "Ao" is also the word used to refer to the color on a traffic light that signals one to "go". However, most other objects—a green car, a green sweater, and so forth—will generally be called "midori". Japanese people also sometimes use the word , based on the English word "green", for colors. The language also has several other words meaning specific shades of green and blue. The native Korean words (Revised Romanization: "pureu-da") or 파랗다 (parah-ta) may mean either blue or green, or bluish green. These adjectives and 파랗다 are used for blue as
Green light source typically has a spectral power distribution dominated by energy with a wavelength of roughly 487570 nm. Human eyes have color receptors known as cone cells, of which there are three types. In some cases, one is missing or faulty, which can cause color blindness, including the common inability to distinguish red and yellow from green, known as deuteranopia or redgreen color blindness. Green is restful to the eye. Studies show that a green environment can reduce fatigue. In the subtractive color system, used in painting and color printing, green is created by a combination of yellow and blue,