Dora the explorer spanish?

My son loves Dora, and is able to use most of her spanish words correctly. There is one word he uses that we can't figure out what he is saying. He uses the word all the time and always says it the same way, so I know he is positive that it is how you pronounce it. The word is "amanatego" or "amanatillo" or something like that. He seems to use it for yellow, and if I say "do you mean amarillo" he says no and gets upset if we change it to that. Any idea what he could be saying?