Why blue? There is no basis for it in the Scriptures. In the Gospel accounts of the Transfiguration—ground zero, as it were, for the onset of this “bright cloud” of agnosia—the cloud is shadow, Jesus’s raiment a “glistering” white. Yet for the past two thousand years, in mosaic after mosaic, painting after painting, Jesus stands transfigured before his witnesses in the mouth of a glowing blue mandorla—a blue almond, or vesica piscus, the shape that, in pagan times, unabashedly symbolized Venus and the vulva.