Orange is the color between yellow and red on the spectrum of visible light. In painting and traditional color theory, it is a secondary color of pigments, created by mixing yellow and red. It is named after the fruit of the same name.
Green is the color between blue and yellow on the visible spectrum. In subtractive color systems, used in painting and color printing, it is created by a combination of yellow and blue, or yellow and cyan. By far the largest contributor to green in nature is chlorophyll, the chemical by which plants photosynthesize and convert sunlight into chemical energy.