Most all of the time that we see auroras it will be the green type. These are produced by oxygen atoms at around 50 to 100 miles high. On some occasions red will also be produced by oxygen but these emissions occur at higher altitudes of 100 to 200 or more miles high and are much less often.
Now, if we mix these red and green emissions, along our line of sight, yellows and oranges will result.
And now add another type of emission that reaches hundreds of miles high, a blue-violet light from the nitrogen molocule, and combine it with the oxygen emissions. The results will be shades of pink or magenta, and various purples or violets. Throw in a sky made blue with moonlight and the result is an ultra-rare multi-colored aurora such as this one on the early morning of November 7, 1998.
I uses a conventional 35mm camera with a 24mm wide-angle lens and Fuji 800 SuperG film for this rare opportunity.