Plato Timaeus 68

These, therefore, are the names we must assign to them: that which dilates the visual stream is white and the opposite thereof black ¹ ; and the more rapid motion, being that of a different species of fire, which strikes upon the visual stream and dilates it as far as to the eyes, and penetrating 68a and dissolving the very passages of the eyes causes a volume of fire and water to pour from them, which we call tears. And this moving body, being itself fire, meets fire from the opposite direction; and as the one firestream is leaping out like a flash, and the other passing in and being quenched in the moisture, in the resultant mixture colors of all kinds are produced. This sensation we term dazzling and the object which causes it bright or brilliant. Again, when the kind of fire 68b which is midway between these ² reaches to the liquid of the eyes and is mingled therewith, it is not brilliant but, owing to the blending of the fire’s ray through the moisture, it gives off a sanguine color, and we give it the name of red. And bright color when blended with red and white becomes yellow. But in what proportions the colors are blended it were foolish to declare, even if one knew, seeing that in such matters one could not properly adduce any necessary ground or probable reason. Red blended with black and white makes purple; 68c but when these colors are mixed and more completely burned, and black is blended therewith, the result is violet. Chestnut comes from the blending of yellow and grey; and grey from white and black; and ochre from white mixed with yellow. And when white is combined with bright and is steeped in deep black it turns into a dark blue color; and dark blue mixed with white becomes light blue; and chestnut with black becomes green. As to the rest, it is fairly clear from these examples 68d what are the mixtures with which we ought to identify them if we would preserve probability in our account. But should any inquirer make an experimental test of these facts, he would evince his ignorance of the difference between man’s nature and Gods—how that, whereas God is sufficiently wise and powerful to blend the many into one and to dissolve again the one into many, there exists not now, nor ever will exist hereafter, a child of man sufficient for either of these tasks. 68e
  Such, then, being the necessary nature of all these things, the Artificer of the most fair and good took them over at that time amongst things generated when He was engendering the self-sufficing and most perfect God; and their inherent properties he used as subservient causes, but Himself designed the Good in all that was being generated.