if an object is made of a material then that object has the properties of that material & a rock is a kind of object & rock is made of minerals ->  rocks will have the properties of the minerals that make up the rocks  the property of something is the same for the things of same kind & color is a property of a material ->  the color property of the same material will be the same  the color property of the same material will be the same & a mineral is a kind of solid / natural material ->  the color property of the same minerals will be the same for the things of same kind  rocks will have the properties of the minerals that make up the rocks & the color property of the same minerals will be the same for the things of same kind -> rocks will have the same color property as the minerals that make up the rocks