A method for coating a moving substrate provides a coating having a chemical composition which varies continuously from the interface with the substrate to the opposite surface of the coating. The method involves directing a vapor coating composition toward a substrate surface and moving portions of the vapor in opposite directions. A vapor coating mixture may include a tin-containing precursor and a silicon-containing precursor. An accelerant, e.g. a phosphorus-containing precursor, may be used with the metal-containing precursors to increase the deposition rate of the coating. The coating deposited on the substrate has regions of continuously varying weight percent of silicon oxide and tin oxide as the distance from the substrate-coating interface increases, with the surface of the coating farthest from the substrate-coating interface being predominantly tin oxide. The regions of varying composition provide the coating with varying indices of refraction to eliminate iridescence to provide a coated article, particularly a tin oxide coated glass article, with a neutral color.