Seurat's palette consisted of the usual pigments of his time such as cobalt blue, emerald green and vermilion. Additionally, Seurat used then new pigment zinc yellow (zinc chromate), predominantly for yellow highlights in the sunlit grass in the middle of the painting but also in mixtures with orange and blue pigments. In the century and more since the painting's completion, the zinc yellow has darkened to brown—a color degeneration that was already showing in the painting in Seurat's lifetime. The discoloration of the originally bright yellow zinc yellow (zinc chromate) to brownish color is due to the chemical reaction of the chromate ions to orange-colored dichromate ions.