There isn't much consistent in anything about the aurora so simplifying any prediction to fit an entire latitude seems very unlikely.
The altitude does in fact have an impact on the colors and yes he's right, it has to do with which elements are present, namely oxygen and nitrogen, and the reason the altitude has an effect is because different levels o the atmosphere have different compositions. A quote from wikipedia: "This is why there is a color differential with altitude; at high altitudes oxygen red dominates, then oxygen green and nitrogen blue/purple/red, then finally nitrogen blue/purple/red when collisions prevent oxygen from emitting anything. Green is the most common color. Then comes pink, a mixture of light green and red, followed by pure red, then yellow (a mixture of red and green), and finally, pure blue."
So yes, it's all about the altitude of where the solar wind is interacting with the atmosphere and nothing to do with its relative position related to the horizon.