In the composite image, above, Anthony sandwiched an image of the all-red totally eclipsed Moon between images of the Moon just before and after totality. Note the fringes of pale blue in those outer Moons.
The blue color is caused by ozone. Atmospheric scientist Richard Keen of the University of Colorado explains: "Most of the light illuminating the Moon passes through the stratosphere, and is reddened by scattering. However, light passing through the upper stratosphere penetrates the ozone layer, which absorbs red light and actually makes the passing light ray bluer." This creates a turquoise-blue border around the red.