Described as a young, handsome man, slim and with fine features, Jaqen H’ghar’s most notable trait is his long hair, red on one side and white on the other after one the fashions in the east. Hailing from th Free City of Lorath, he is first met as a chained and caged prisoner being taken by Yoren to the Wall. Rorge and Biter, his companions in the cage and in the black cells before it for unknown crimes, are brutal murderers but for some reason are afraid of him. He speaks the Common Tongue of Westeros, but with odd syntax, eschewing pronouns (e.g. “A man could use another taste of beer. A man has a thirst, wearing these heavy bracelets.”)
It seems the production attempted to stay quite faithful to the character. Wlaschiha has referred to having a red-and-white wig, though it may be that rather than being half and half, they’ve put streaks of white through it. He’s also noted that the way the character speaks in the novels has been carried over into the series. The only real difference we can find is the fact that he’s almost 40 years old, certainly older than Jaqen as described in the novels.