Where is imagery found in marigolds?

Imagery in the text:

When I think of the hometown of my youth, all that I seem to remember is dust—the brown, crumbly dust of late summer—arid, sterile dust that gets into the eyes and makes them water, gets into the throat and between the toes of bare brown feet.

And one other thing I remember, another incongruency of memory—a brilliant splash of sunny yellow against the dust—Miss Lottie’s marigolds.

For the most part, those days are ill-defined in my memory, running together and combining like a fresh watercolor painting left out in the rain.