Brown is made of green and orange. According to Color Matters, both green and orange are secondary colours, which are created by combining two basic colours. Any two secondary colours can be combined to produce a brown tint, ranging from muddy brown to olive brown.
Depending on the hues of green and orange, brown will take on a specific hue. Dark hues produce a darker, more olive-colored shade of brown, while light colours produce a light, yellowish brown.
Green or orange may create a tertiary colour when combined with a primary colour, but brown is always the result of combining two secondary colours, regardless of hue or brightness.