What are the settings in the poem "What Is Red?" by Mary O'Neill?

Setting refers to the time, place, and environment in which events in a piece occur or unfold. As such, it also includes aspects such as a historical period, timing, geographical location, circumstances, and conditions which a piece of writing relates to or covers.
"What is Red?" by Mary O' Neill does not have a particular setting in this sense. The poem explores the different meanings that red has by asking and then answering the question, which is also the title of the poem.
The speaker responds to the question by providing the reader with a series of associations which red has in different contexts. The list refers to the common symbolic meanings linked to the color. It is clear that each meaning is associated with its context. In this sense, then, one could say that there is a setting because the word is contextualized within such event, time, or place.
In the first stanza, the speaker mentions nine contexts: sunset; being courageous in a situation that demands action; getting sunburned; the sheer depth of color one sees when admiring a rose; an injury which leads to bleeding; observing the color of a building block; being at a concert; the sensation one feels when embarrassed; seeing the simple colors of certain objects—specifically ones associated with danger; and an incident wherein one becomes angry, which causes a rush of blood and brings on a headache.
In the second stanza, the speaker once again relates red to seven conditions: as a description of an American native; a symbolic heart signifying love; a circus where one would find a cart with red decorations; a form of make-up; hearing a warning or the expression of anger; a sign that symbolically gives a warning; and a large ball, probably found at the beach. All these descriptions of red are conventional and reasonable.
The speaker moves away from the generally accepted connotations that red has and presents an opinion by stating that

Red is the giant-estColour of all.

and

Red is a show-off,No doubt about it –

The speaker is clearly impressed by the color red and then, by asking a rhetorical question, suggests that one cannot imagine life without it.