Herrick packs a whole view of mortality into six lines and a single comparison. The opening statement works almost like a definition: "Life is the body's light." Everything else depends on it. If life is a light, then the colours of a living face, the flush of the cheeks and the red of the lips, don't belong to the body itself. They are effects of that light, just as a sunset's colours depend on a sun that has not yet gone. Take away the source and the colours go with it.
The poem is built as three rhymed couplets (declining/shining, air/are, place/face) in a rhythm close to iambic pentameter. The couplets are tidy and closed, which suits an argument that moves like a proof. The first couplet has an extra unstressed syllable at the end of each line, so the verse seems to trail off just as it speaks of fading. The word "declining" is poised between body and sky. A sun declines, and so does a failing life, and Herrick lets the word cover both before the comparison is spelled out.
That comparison is the poem's engine, and it works in both directions. The cheeks and lips become "crimson clouds," so a human face is turned into a sky. Then the sky is described in the language of cloth: "counter-changed tabbies in the air." A tabby was a rippled, shimmering silk, and "counter-changed" has a heraldic ring, suggesting colours that swap places and interweave. The phrase makes the evening sky seem luxurious and constantly shifting. A living face is also changeable, with its blushing and paling, and Herrick seems to want that restless variety in our minds before he takes it away.
He takes it away flatly: "The sun once set, all of one colour are." The line has none of the previous line's rich texture. The inverted word order, forced by the rhyme with "air," holds the weak verb "are" at the end like a full stop, and "one colour" is the opposite of "counter-changed." The word "once" also appears twice, in "once declining" and "sun once set," quietly tying the body's light to the sun's. Death, like sunset, happens once and cannot be undone.
The last couplet turns back to the body with a brisk "So," and the vocabulary darkens. "Fresh tinctures" suggests newly mixed dyes or pigments, and the word "fresh" stresses how recent and delicate the colour was. They "lose their place," as if each shade had a position it was forced to give up. Then comes the heavy, clotted line "And dismal darkness then doth smutch the face." The repeated *d* sounds fall like a thud, and "smutch" is the most striking word in the poem. It means to smudge or blacken, as with soot, and it is an ugly, almost domestic word. Herrick could have chosen something grand like "shroud" or "veil." Instead death is a grubby smear across a once-bright face, which makes the ending feel more physical and less ceremonial.
Notice also the shape of the whole. The poem moves from body to sky and back to body, but the sky does not return in the final couplet. Only the face is left, darkened. The comparison has done its work and disappeared, and the reader is left with the thing it was describing.
What makes the poem worth reading is its unsentimental compression. Judging by the text, there is no consolation here. It mentions no soul, no afterlife and no grieving speaker, only the plain fact that colour and variety leave the face when life does. Sunset is usually treated as one of the most beautiful moments of the day, but Herrick looks past it to the moment after, when the show is over and the sky is a single dull shade. The poem shows how an extended image can carry an argument in a handful of lines. It also leaves a lingering effect, because the next time you watch colour drain from an evening sky, it is hard not to think of a face.