Tortoise beetles can undergo rapid color change. Edward Barrows* observed these beetles in the laboratory and noted that they could change color from brownish orange with black spots to a metallic gold in as little as 120 s. If disturbed, gold beetles will turn from brilliant gold to orange in as little as 12 s. The color change is controlled by the moisture content of the elytra. Pinned, dried, specimens are never gold. Typically, golden tortoise beetles mate when they sport their brilliant gold, or will turn gold soon after the mating process begins. The change in color may have a role in signaling to mates (gold) and potential predators (orange and black).
*Edward M. Barrows. Life Cycles, Mating, and Color Change in Tortoise Beetles. The Coleopterists Bulletin, Vol. 33, No. 1 (Mar., 1979), pp. 9-16