Interestingly green is not always green in Japan (and some countries). For instance, a green traffic signal is called blue one in Japanese not only because its color is sometimes close to blue but blue means green in some cases. It is said that there were only four colors in ancient Japan. Red(aka) and black(Kuro) meant bright(akarui) and dark(kurai). White and blue meant clear and haze. I’m not sure it is true or not but it sounds interesting.
One of the most strange expressions in Japanese would be “green colored black hair” which has the origin in an old poem in Chinese. When we come to be elderly people, the color of our hair would be silver. So, you may think younger people have green hair like new leaves.