Pollia condensata produces its blue color at the nanoscale level and is more intense than anything ever studied. From the Smithsonian Magazine:
When they examined P. condensata on a cellular level, they realized that the fruit produces its characteristic color through structural coloration, a radically different phenomenon that is well-documented in the animal kingdom but virtually unknown in plants. They determined that the fruit’s tissue is more intensely colored than any previously studied biological tissue—reflecting 30 percent of light making it more intense than even the renowned color of a Morpho butterfly’s wings.
Most plants produce a pigment which coats the plant but is not a part of its cells. When the plants die they no longer produce the pigment and fade in color. Not the amazing blue of P. Condensata.