Dickinson turns the colours of the natural world into a household account book. In eight lines, Nature becomes a careful manager of her supplies, handing out some colours freely and rationing others. Yellow is the rationed one. She "saves" it for sunsets, while she is "Prodigal of Blue." The poem is about color on the surface, but its real subject is value: the things we treasure are often the things that are held back.
The vocabulary of money runs through the poem. Nature "uses," "Saves," is "Prodigal," is "Spending," and "affords." Yellow comes "scantly," a word that sounds as thin as the supply it describes. "Prodigal" is the sharpest choice. It means wastefully generous, and it may recall the biblical prodigal son, so blue seems almost reckless in its abundance. Judging by the imagery, blue is the colour of things Nature has in huge quantity, such as sky and sea, though the poem never says so. Yellow, by contrast, is a luxury that even Nature, who might seem to have limitless resources, can only just "afford."
The form supports this idea of economy. The poem is two quatrains of short lines, close to a hymn or ballad stanza but stripped down. The rhythm is mostly trochaic, with the stress falling on the first syllable: "NA-ture RA-rer U-ses YEL-low." Lines two and four are even shorter and end on a stressed syllable, "Hue" and "Blue," so they close with a snap, like a purse shutting. Those two words also rhyme, and it is tempting to read that as telling: "Hue" is the general word for colour, and it is paired with the colour Nature spends most freely, as though blue were the default. The second stanza rhymes "affords" with "Words," but only roughly, so the ending sounds slightly off-balance. Lines one and three of each stanza do not rhyme at all, which leaves the poem sounding spare rather than polished.
Dickinson's syntax is compressed too. "Saves she all of that for Sunsets" flips the usual word order, which gives the line a slightly formal, old-fashioned ring, as if Nature were being reported on by a clerk. And because the lines run on without punctuation, "Sunsets" slides straight into "Prodigal of Blue," so thrift and extravagance sit side by side with no pause between them. The capitalised nouns (Yellow, Hue, Scarlet, Woman, Lover's Words) turn colours into named, almost personified things, each with its own price and character.
The comparisons in the second stanza are the most interesting part. Scarlet is spent "like a Woman," a phrase that now reads as a dated stereotype of the extravagant spender, though it works here to suggest something showy and freely given. Yellow, however, is handed out "Only scantly and selectly / Like a Lover's Words." The poem moves from outward display to inner feeling, from a flashy colour to the guarded things people say to those they love. "Selectly" is an unusual-sounding adverb, and it suits the idea of words chosen with care, each one weighed before it is released. The suggestion is that a lover who says little makes each word count for more. Scarcity gives weight, and a sunset glows more because yellow has been saved for it.
The poem also practises what it describes. It uses very few words and gives away its meaning only in the last two lines, when the lover's words arrive. A reader who has been thinking about paint and sunsets suddenly finds the poem has been about speech and affection all along.
That sudden widening is what makes the poem worth reading. Dickinson takes an ordinary observation about colour and turns it into a quiet argument about restraint, about how little is sometimes enough to carry great feeling. She does it in a form so small it fits in the palm of a hand, and the compression becomes part of the argument: the poem itself is rare, selective and carefully spent.