The simple answer to your question is "no." There isn't one accurate description anywhere in the novel. Let me tell you, I tossed and turned over your question. This is my very favorite book to teach, and I was floored that I was stumped by this. You see, for me, Daisy will always be Mia Farrow and Gatsby will always be Robert Redford. I suppose my mind clung to the visage from the movie because of the purposeful lack of description in Fitzgerald's novel of genius. But I digress . . .
Let's focus on what is said about the two characters. Then perhaps we can approach that analytical one for both that you need so desperately. In regards to Daisy, I think Fitzgerald does a good job with his original physical description:
Her face was sad and lovely with bright things in it, bright eyes and a bright passionate mouth, but there was an excitement in her voice that men who had cared for her found difficult to forget: . . . a promise that she had done gay, exciting things just a while since and that there were gay, exciting things hovering in the next hour. (9)
Further, there are numerous times in the book where Daisy's face is described as "white." One example is the flowing and billowing white curtains surrounding Daisy as Nick first sees her. Another is the flashback where Daisy and Gatsby first kiss. Here is yet another example where white is used in regards to Daisy:
Sometimes she and Miss Baker talked at once, unobtrusively and with a bantering inconsequence that was never quite chatter, that was as cool as their white dresses and their impersonal eyes in the absence of all desire. (12)
Gatsby, of course, is another story. In regards to the purely physical, I would suggest a few short sentences in Chapter 3 when Nick finally meets Gatsby (and right after he uses his very prominent "Old Sport" phrase to describe Nick as well as anyone else):
He smiled understandingly--much more understandingly. . . . Precisely at that point it vanished--and I was looking at an elegant young roughneck, a year or two over thirty, whose elaborate formality of speech just missed being absurd. Some time before he introduced himself I'd got a strong impression that he was picking his words with care. (48)
In my opinion, the best description of Gatsby is a few pages into Chapter 4:
This quality [balancing himself on the dash board of his car with resourcefulness of movement] was continually breaking through his punctilious manner in the shape of restlessness. He was never quite still; there was always a tapping foot somewhere oar the impatient opening and closing of a hand. (64)
In regards to Gatsby's words or, even better, how Gatsby speaks, there is light on the very next page:
He looked at me sideways--and I knew why Jordan Baker had believed he was lying. He hurried the phrase "educated at Oxford," or swallowed it, or choked on it, as though it had bothered him before. (65)
In regards to every single example quoted here, I keep asking myself, "Is this even a physical description?" You see, this is the beauty of Fitzgerald's genius: to add one small idea, one small step at a time so that our image of these characters is continually shaped by the formless wealth around them. Furthermore, the longer I think on this subject the more I think that Fitzgerald has us playing right into the palm of his hand, . . . ironically Fitzgerald spent his life playing right into the palm of Zelda.