I m going to agree with you that there are too many distinctions and that grey eyes are a form of blue and amber eyes are the lightest shade of brown however your theory of blue green hazel and brown being enough is incorrect as true hazel eyes are just simply a light golden brown slightly darker than amber and the definition you ve given hazel eyes green and brown makes them fall under the green category So I say there are only 3 true eye colors blue green and brown the rest or significantly different shades mixes of the 3