Alexander the Great, quite possibly the most famous Greek ever, was described as blonde, and possibly with one blue and one brown eye. So its pretty unquestionable that there were fair haired, light eyed, and presumably fair skinned greeks, particularly at a time before all the persian invasions starting 500 BC or so. Troy and the Trojan war, presumably the city in Turkey, would have happened centuries earlier, well before significant ethnic exchanges via invasion. Its even more likely that having blonde hair and light eyes, almost ALWAYS an exceptional set of features anyplace outside of northern europe, would have contributed to Helen's extraordinary beauty in Greece. We can be HIGLY confident that however she looked, it certainly wasn't sub-Saharan black, as those folks were specifically called out whenever they appeared due to the extreme exoticism of their appearance.
Though I'm more bummed about Achilles, the GREATEST WARRIOR of the saga, being a 120 pound twink, if the Ellen Page casting is true. Though maybe she hit the T really hard and bulked up? Achilles actually being a woman and not having testicles might actually be a fun way to play into the "Achilles Heel" myth, since a blow to the groin wouldn't hurt her like it would a man