AstroLAB's Interesting Tables    
Colours of Aurorae    
Wavelength (nm) Emitting Ion, atom or molecule Height (km) Visual Colour
391.4 N+ (nitrogen ion) 1000 violet-purple
427.8 N+ (nitrogen ion) 1000 violet-purple
557.7 O (oxygen atom) 90 - 150 green
630.0 O (oxygen atom) > 150 red
636.4 O (oxygen atom) > 150 red
661.1 N2 (nitrogen molecule) 65 - 90 red
669.6 N2 (nitrogen molecule) 65 - 90 red
676.8 N2 (nitrogen molecule) 65 - 90 red
686.1 N2 (nitrogen molecule) 65 - 90 red
       
Source: The Cambrdige Encyclopedia of the Sun (Kenneth R. Lang)