"The paths pursued by those great examples must become yours, young gentlemen, or you can neither be eminent in colouring, nor sure in the execution of your art. It is possible, that by habits of practice, handed over from one to another, or by little managements in laying colours on the canvass, where little or nothing of the general science has been studied and attained, many may so far succeed as to avoid glaring errors, and a violation of those first principles which have their foundation in nature. But that success is at all times extremely hazardous and dependent on chance. More frequently it has introduced invincible conflicts between the primary and secondary colours, to the ruin of harmony and aerial perspective, and to the overthrow of the artist, whenever the picture is glanced upon by the eye of scientific discernment. Contemptible are the best of such managements, ever in the hands of those that know them best, compared with a full and masterly possession of the philosophy by which this part of your art must be guided. If the ordonnance of colour, on each figure and on the whole, is not disposed according to the immutable laws of the science, no fine effect, or accordant tones of colours, can possibly be produced. There is, therefore, but one way to make sure of success, and to raise your characters in this point, and that is by making yourselves masters of the whole philosophy of colours, as Titian and Correggio did, and some others, in whose works, from first to last, the minutest scrutiny will never find a colour misplaced or prejudiced by its disposition with others.