Descriptions of Herakles include:
"Hieronymus (of Rhodes) the philosopher describes the make of his body, as tall, bristling-haired, robust"
"Dicaearchus (student of Aristotle) says that he was square-built, muscular, dark, hook-nosed, with greyish eyes and long hair"
Descriptions of the Ancient Greeks themselves were typically dark haired, some with fair hair and the occasional red head, though it is relative as if you have dark hair then someone with light brown hair would look fair to you and if you lighten dark hair it oftens goes a reddish colour.
Skin tones were described as being lighter than Egyptians, but darker than those Europeans living further North.
Statues, Roman copies of paintings and most evidence from their writings show them having dark hair and various shades of tanned skin, women being generally paler skinned.
Basically they looked a lot like modern Greeks, so the majority had olive skin and dark brown hair, getting lighter colouring as you move North.
Some of the Gods were said to have fair hair, some dark hair, however descriptions could vary from place-to-place and over time, but I do not recall any descriptions of blue-eyed Gods. They all pretty much resembled Greeks - man creates God in his own image, so the Greek Gods appearing remarkably like Greeks is not particularly surprising.