Arthur has fair skin color, and have pale yellow eyes and pale blond hair. He seems to always favour wearing his armour, which changes color with the personality Arthur presently has (which varies).
However, depending on his mood and attitude, his eyes colour changes corresponding to them. When he is calm and friendly, he has a soft and warm aura and appearnce, giving off a kind individual with green eyes. His armour also changes to be a comforting sight, and welcoming.
However, if his more darker and sinister personality began to surface, he will go under a transformation of sorts. His eyes will go to a pale golden color, and his expression darkens. His armour will turn black, and his markings will become red. This also attributes to his sword as well, changing its physical appearance with the personality of Arthur.