Daniel Radcliffe has the dark hair described in the books; however, in the book “Deathly Hallows,” Harry’s hair grew shoulder-length due to his preoccupation with finding the Horcruxes, something they don’t show in the film. The other notable difference is Radcliffe's blue eyes, which don't match his literary counterpart's green ones.
The only physical feature that Rupert Grint and Ron Weasley shared was the signature red hair. Ron was described as "tall, thin and gangling, with freckles, big hands and feet, and a long nose," while Grint has blue eyes, is freckle-free, and at 5’8” is below average in height.
Ralph Fiennes’s creepy portrayal matched Rowling’s description of Voldemort as “tall and skeletally thin” with a face “whiter than a skull” and a nose “flat as a snake’s with slits for nostrils.” However, Fiennes’s blue eyes were kept as-is instead of changing them to scarlet.
While Helena Bonham-Carter’s wild, curly hair wasn’t a feature in the books, it helped to sell Bellatrix’s craziness. Bonham-Carter also wasn’t as gaunt as Rowling described in the books after her time at Azkaban, but did portray her air of arrogance perfectly.
Rowling’s Dumbledore had “light” blue eyes and his beard was “silver [...] long enough to tuck into his belt.” Richard Harris’ hair was more white than silver and he had darker blue eyes, while Michael Gambon’s eyes were brown and his beard was a few inches too short to be tucked into his belt.