Zebra stripes make a simple picture here: black, white, black, white, repeated like a chant. The poem looks at the animal's pattern and sees a kind of strict order. The stripes are "aligned" and "symmetrical," and the "pristine hairline" between them never wanders. Even the line breaks feel tidy and measured, which fits the subject.
The speaker seems to admire the pattern, but also to be a little unsettled by it. The last lines carry the weight: gray is "never even a shadow option." Gray stands for the in-between, the blurry and uncertain, and the zebra's coat has no room for it. Read that way, the poem hints at how people sometimes want the world sorted into two clean sides, with no middle ground.
The mood is cool, precise, and slightly stark. It feels calm on the surface, yet the rigid contrast leaves a faint chill, as if the neatness has a cost.