The Swiss-born Nicolas Party often quotes Paul Gauguin—“I only want to make simple art.” But Party’s art isn’t simple. Working in a make-believe color palette, he paints fantasias that frequently refer to important past works and artistic movements. In “Stage Fright,” Party has been commissioned to make a monumental site-specific work in the Kestner Gesellschaft’s large domed hall. His goal is to create a green grotto, based on historic paintings of underground caves. Questions about the relationship between light and color are at the heart of this show. —E.C.