Brown is made from green and orange. Color Matters says that green and orange are both secondary colours, which means that they are made by mixing two primary colours. You can get any shade of brown by mixing any two secondary colours, from muddy brown to olive brown.
How green and orange mix to make brown depends on how green and orange are mixed. When you mix light colours together, you get a light, yellowish brown. When you mix dark colours together, you get a darker, more olive brown. When you mix green or orange with a primary colour, you might get a tertiary colour, but when you mix two secondary colours, you always get brown, no matter what hue or brightness you use.