Morpho menelaus and Phoebis philea - a pair of jaw-droppingly beautiful and bright butterflies from Brazil and Peru respectively.
Because the colouring of the Morpho comes from refraction rather than pigmentation it will never fade, and Phoebis philea, a pierid, will retain its bright yellow for many years as well.
Some internet wisdom to explain this is below - but you can see how the refractive properties generate the astonishing colouring by viewing it from different angles, where it will be seen to change from a deep blue to violet, and then to an almost see-through pearl.
The microscopic scales covering the morphos’ wings reflect incident light repeatedly at successive layers, leading to interference effects that depend on both wavelength and angle of incidence/observance. Thus, the colours appear to vary with viewing angle, but they are actually surprisingly uniform, perhaps due to the tetrahedral (diamond-like) structural arrangement of the scales or diffraction from overlying cell layers. The wide-angle blue reflection property can be explained by exploring the nanostructures in the scales of the morpho butterfly wings. These optically active structures integrate three design principles leading to the wide-angle reflection: alternative lamellae layers, Christmas tree-like shape, and zigzag pattern of the ridges. The reflection spectrum is found to be broad (about 90 nm) for alternating layers and can be controlled by varying the design pattern. The Christmas tree-like pattern helps to reduce the directionality of the reflectance by creating an impedance matching for blue wavelengths. In addition, the zigzag pattern of ridges destroys the unwanted interference for other wavelengths in wide angle.
If you would prefer to have specimen label cards in the frame, please let me know. They are displayed in my new type of frame which can be opened.