I was watching my least favorite episode of Korra (episode 4- I forget the title, but it was the one where Korra refused to admit she was afraid until she finally did) and in one of the scenes Amon did appear to have the amber eyes typical of firebenders. Of course, it's possible to descend from benders and not have the ability to bend. Personally, I don't think he is Mako and Bolin's father, but we shall find out in eight days I suppose.