Light, then, contains within itself all colors. When light falls upon an object, for example, a leaf, the latter absorbs some of the colors of the light and throws off others. The part thrown off in the case of the leaf is what we call its color: green, or it may be greenish yellow, or a bluish green, or in autumn, crimson. Every substance has this power of absorbing some of the light and of throwing off the rest; and it is the different chemical properties of different substances that decide which of the colors of light they will absorb and which they will throw off; or, as we say, causes them to be a certain color.