The index of refraction of air for red is 1.000292 and that for blue is 1.000295. Out of a total refraction of about 0.53°, the dispersion is only 0.006° or about 20 arc seconds, compared to a 120 arc sec resolution for the eye. Thus under normal conditions the eye would not see the separation of red and blue images of the sun.
The green or blue would be seen only after the red image is gone, and the passage time for this 20 arc second band is reported by the Meinels to be about 1.4 seconds.
The successive red, green, and then blue images can be seen more distinctly by viewing the planets Venus and Jupiter with a telescope as they pass below the horizon. The ease of viewing the colors in these cases has to do with their smaller angular diameters.
At right is a rough sketch of the color separation in a photograph of Venus reproduced in Greenler's "Rainbows, Haloes and Glories". It is described as a photograph taken by Raymond F. Newell, Jr. in New York when Venus was 2 to 3 degrees above the horizon. Also displayed there is a photograph taken when Venus was 10 degrees above the horizon which has a very different appearance. At 10 degrees the upper portion is bluegreen, with a thin green region, a white region, a yellow region and then a very thin red edge on the bottom.
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