The makers of Game Of Thrones have tried to stay as faithful to George R. R. Martin's books as possible, but some changes simply must be made when a book is translated into a visual medium.
Characters are often changed to make them, and their appearance, more visually appealing to viewers, which is why that imp Tyrion Lannister is still a sympathetic character:
“Tyrion’s fingers went to the great gash that ran from above one eye down to his jaw, across what remained of his nose. The proud flesh was still raw and warm to the touch.” —A Storm of Swords
And some characters have their overall look radically altered just so their flamboyant style will flow with the overall color scheme of the show, such as the radical decolorization of Daario Naharis:
“Daario Naharis was flamboyant even for a Tyroshi. His beard was cut into three prongs and dyed blue, the same color as his eyes and the curly hair that fell to his collar. His pointed mustachios were painted gold. His clothes were all shades of yellow; a foam of Myrish lace the color of butter spilled from his collar and cuffs, his doublet was sewn with brass medallions in the shape of dandelions, and ornamental goldwork crawled up his high leather boots to his thighs.” —A Storm of Swords