To put it bluntly, Jack is described as unattractive. Golding tells us that he has a tall, lanky build and that he is “thin and bony.” He has red hair, a freckled face that is described as “crumpled.” The phrase “ugly without silliness” is used to describe him. That implies that he is ugly without any endearing features to redeem his appearance. He has pale blue eyes, which are described as quick to flash with anger. Since Jack quickly adopts the role of antagonist in this story, his fiery red-headed appearance seems to fit with this.
A distinction develops between the way the other boys see Jack and how he is seen by readers of the book and the officer at the end of the book. Readers may see Jack as a gangling boy wearing rather silly clothes. To the other boys, however, he appears to be a ruthless savage.