Process of elimination would mean she’s talking about autumn, specifically the colors of autumn from white to black, to red, and yellow-green and dark green. It seems she is writing from the point of view of nature (apostrophe) as she wonders what is happening to the world as the seasons colors begin to change and she must wear “Cuffs of Chrysolite” into the evening.
Autumn is the time for reflection when after the long summer the leaves turn, the sky darkens earlier each evening, and we begin to watch the sky for signs of snow. Perhaps Emily wrote this poem in response to the end of the warm season, perhaps there had been a day in particular that was colder than usual and so she imagined what the earth itself must think as it looks in the mirror and notices it is wearing a dress of a new color.
What’s unusual is that nature seems to be confused, as if she has never experienced an autumn before but has experience with “Summer”, “Spring” and “that long town of White” (the snows of winter). Autumn is usually portrayed as the time of harvest when, as Keats writes, “barred clouds bloom the soft-dying day, / And touch the stubble-plains with rosy hue” and so there is usually an abundance associates with this season, yet here it seems to be a period of forgetfulness and where the days live so short that the sun “shuts my question down” because it doesn’t have time to answer her questions. And in the end she seems as if she is forced to wear a new dress – in one version she wears “clasps of Chrysolitte” which gives the impression of her being chained or imprisoned, and in this version she wears “cuffs” which alludes to dress. Either way she seems to be forced into this season, as if the autumn harvest wasn’t an occasion of bounty and joy but of people and even the sun taking what they want from her and then leaving her barren. In other words, Autumn seems to be portrayed as a mother who child is taken from her every year and , perhaps from absolute grief, she dies in winter so that she can forget the pain of the harvest.