Like many bat-pollinated flowers, Cippocereus flowers begin to open at night. Though the sepals and hypanthium are a beautiful blue, the flower itself is cream-colored (easier to see in the dark night) and produce prodigious amounts of nectar for its obligate bat-pollinators.

Blue Cacti & Bat Pollinated Flowers — Crime Pays But Botany Doesn’t

You have to take a look at the amazing blue cacti and their flowers. Just beautiful!