There is always variation in a particular color from batch to batch. Besides, the SP used several shades of scarlet over the years. It also depended on whether it was enamel like Dulux or a isocyanitic polyurethane like Imron. The SP didn't buy paint from the same manufacturer all the time, so this can lead to differences in hue and value too. Nor is there perfect pitch for color as there is for sound. Color perception is also influenced by the surrounding background and lighting temperature.