What was most apparent as the eclipse deepened was that the leading edge of the umbra appeared bluer than the deeper reddish umbral section. This is typical of an eclipse where the Danjon value (a scale that evaluates the color of total lunar eclipses) equals 4, which occurs when Earth’s atmosphere is clear of contaminants (such as volcanic aerosols). The blue collar, as shown in Image 3, is caused by light passing through the clear upper stratosphere and penetrating the ozone layer, which absorbs red light, thus making that section of the shadow appear bluer. Close inspection also revealed the deepest penumbral shadow causing a yellow band to appear beyond the blue one.
There was also something else at play, which made it difficult to judge the overall intensity of the shadow’s color. In Image 3, note how the southern highlands (at the top) appear so much brighter than the remainder of the disk in shadow. This is not due to irregularities in Earth’s atmosphere, but rather due to albedo effect. Lunar highlands reflect twice as much light as the darker maria, which dominate the shadowed region.