“Levin had called Klein’s blue paint ‘cheap poster-paint.’ Musgrave corrected him in a letter to the editor, pointing out that Klein ‘prepares and grinds his own paint, an exacting process which gives it its own especial depth, brilliance and beauty.’ This was Klein’s ultramarine blue, in which the radiance and intensity of the original dry pigment was not compromised or dulled by the medium binding it to the support.”