The poem’s imagery summons up the dreamy, "pale gold" perfection of Renaissance art and the ripe, "fruit-like" loveliness of a young woman—fragile visions of beauty cracked around the edges by hints of violence.
The speaker's imagined portrait of the lady draws on a thorough knowledge of Italian Renaissance art. He returns and returns to the idea that all her beauty should be displayed against a "background of pale gold"—words that might evoke the otherworldly gilded backdrop of a painting by the Renaissance artist Giotto or the "pale ground" of a Botticelli sky. This ethereal color frames the lady as if she were a saint, suggesting that there's something transcendent about her loveliness. She can’t appear against any old landscape: her beauty must look as if it's part of another, better world.
In his imagination, the speaker experiences the lady's beauty not just as a sight, but as the hint of a delectable flavor. His vision of "honey-coloured" hyacinth buds pressing themselves against the lady's mouth doesn't just paint a picture of golden blossoms but also of a sweet, nectar-scented kiss. Similarly, her "fruit-shaped" chin is round, soft, and ripe—and ripe for the plucking, too. Clearly, the speaker would love to take a bite out of this lady, to devour her with his mouth, not just his eyes.
He's fascinated by her delicacy, too. When he pictures her "lithe neck," suggesting it's so small that "three fingers might surround" it, he's clearly exaggerating, as the reader who tries making a circle with their first three fingers can see—one couldn't encompass a baby's neck that way, let alone even the most petite of adult women's. This image thus does several things at once. It suggests that the speaker has an impossibly idealized vision of this lady; it conjures up an exquisitely small portrait, in which three fingers might actually encircle the painted neck; and it introduces an unnerving hint of violence. An easy neck to grip is an easy neck to throttle.
These images suggest that the speaker's worshipful fascination—the lady is a perfect saint, a virginal Madonna, a dainty angel—goes hand in hand with a barely contained desire to gobble her up.