A zebra's stripes are meant to make it stand out, yet the poem opens with the odd idea that being distinct can work against you. As the speaker tries to look closely, focus turns painful, a strain that grows at the edges of thought until the mind simply gives out. Then the stripes begin to blur. Black and white run together and swallow each other, and even the viewer's eye, which the stripes once held in place, loses its grip.
The final lines name the result plainly: colors streak, lines waver, and the sharp opposites boil down into "an easy shade / of seeping gray." The word "easy" suggests relief, but also surrender. The mood is tired and quietly uneasy, like watching clear differences dissolve through overload or exhaustion. The poem seems to ask what is lost when everything sharp becomes the same muted middle.