Object-colour manifold

Colorimetry can predict which lights will look alike. Such lights are called metameric. Two lights are metameric if they have the same tri-stimulus values. Using the tri-stimulus values as Cartesian coordinates one can represent light colours as points in a 3D space (referred to as the colorimetric space). All the light colours make a tri-dimensional manifold which can be represented as a circular cone in the colorimetric space. Furthermore, colorimetry also claims that reflecting objects illuminated by the same light will look alike as soon as they reflect metameric lights. All the object colours are then represented as a closed solid inscribed in the light colour cone provided the illumination is fixed.