What does Captain Beatty in Fahrenheit 451 look like physically?
The interesting thing about Beatty is that we don't get a direct description of his appearance, so we have to make guesses, based on other clues. The first inference that we can make is when Bradbury is describing Montag at the beginning of the book. Bradbury says that Montag has "the fierce grin of all men singed and driven back by flame." Because he uses the words "all men," we can apply this to Beatty also. Bradbury also describes Montag as "burnt-corked," and as having a "fiery grin" that had always been there for as long as he can remember. If we take these descriptions, and draw parallels to Beatty, we can assume he is also a man who has a fierce grin, and who looks, like Montag, slightly burnt and dark from his job working with fire. This is confirmed later when Montag is in the firehouse looking around at Beatty and the others, and describes them as
"men whose faces were sunburnt by a thousand real and ten thousand imaginary fires, whose work flushed their cheeks and fevered their eyes...they and their charcoal hair and soot-colored brows and bluish-ash-smeared cheeks where they had shaven close."
He is startled to realize that he had never met a fireman who didn't have dark hair, eyes and skin, who was close-shaven but looked stubbly from the ashes. So, we can conclude that Beatty fits in this category also. The only specific description of Beatty comes as Montag enters the firehouse for the first time. The text states that Beatty is holding cards "in his thin hand." So, Beatty has dark hair, eyes and skin, thin hands, and intense eyes.
I hope that helped a bit; good luck!
Is he even a guy?
There really aren't many specific physical descriptions in Fahrenheit 451 for most characters, including Beatty. However, there are descriptions of firemen in general. They all have "black hair, black brows, a fiery face, and a blue-steel shaved but unshaved look" (pg. 33). There is, however, one aspect that is directly applied to Beatty. He is described to have a "pink face burnt and shiny from a thousand fires and night excitements" (pg. 39).
Also, because Beatty is more experienced than the other firemen, and is their captain, we can assume that he is most likely older than the others. This meaning that his facial attributes show to be less youthful and more aged than those of Montag's.
Hope it helps. :)