Describe the main characters: what do they look like? What are they like?

Regarding the first part of the question that asks what Tom Canty and Edward Tudor look like, the story gives readers almost zero information about what they look like. We aren't even given an eye color for either boy. What readers are specifically told is that the two characters look practically identical.

Thou hast the same hair, the same eyes, the same voice and manner, the same form and stature, the same face and countenance that I bear. Fared we forth naked, there is none could say which was you, and which the Prince of Wales.

While Tom and Edward might look identical, they most certainly are not very much alike in other regards. Tom is everything that you would want in a friend and/or king. He's patient, kind, loving, and looks for ways to make a situation better for others. He's also someone that dreams of a better world.

His head grew to be full of these wonderful things, and many a night as he lay in the dark on his scant and offensive straw, tired, hungry, smarting from a thrashing, he unleashed his imagination and soon forgot his aches and pains in delicious picturings to himself of the charmed life of a petted prince in a regal palace.

Edward, on the other hand, is a jerk through most of the story. He's ignorant of how the world outside of the palace actually works. He's extremely proud, and very selfish. He believes that the world exists for his benefit and pleasure, and he looks for ways in which a situation can benefit him. Thankfully, by the end of the story, Edward is a much reformed person that then uses his royal powers for good instead of for himself or threatening other people.