The speaker in this poem is talking to a "housewife in the evening west" - symbolically, talking to the on-coming sunset as it sweeps (with "many-colored brooms") across the sky from east to west. As the colors of the sunset progress across the sky and are reflected in a pond, the speaker comments on the changing spectacle. Purple in the sky and reflected in the water may simply describe one of the colors of the sunset. Historically, purple was reserved for royalty or very wealthy individuals, so the speaker may also be considering that someone responsible for cleaning the evening sky must be very powerful. In the same way, amber and emerald green may identify other colors seen in the surroundings or may refer to the wealth of natural riches being observed.