Some comic books provide the only note of color— of a certain color. They lie
Our speaker goes back to critical mode. Instead of, say, flowers adding color to this greasy scene, the speaker observes that comic books are the only colorful things here.
When she writes "a certain color," she may as well be saying, "it's kind of colorful, but not really."
She might also be implying that it's easy to tell what color these comic books are for sure, but everything else is so covered in grease that it's hard to tell what color things were originally. So compared to that of the other stuff at the station, the color of these comic books is certain.
Comic books might also be a tiny dig at these people, by implying that they aren't perhaps "serious" readers. They aren't reading novels or newspapers.
upon a big dim doily draping a taboret
A taboret is a small, portable table. Think of it as a cabinet or storage cart, like this one.
And a doily is a decorative piece of lacey fabric that's typically draped over a table. They're very girly (not to make sweeping generalizations or anything), with intricate, white lace work.
So the comic books are lying on this dim (notice: not colorful) doily on a small worktable in an interesting mash-up of the masculine and feminine. We've seen the men in this family, but where's the lady? Who draped the doily over the table?
Also, we can't help but notice that doily rhymes with oily, and we've seen an awful lot of oil in this poem. Once again, Bishop is drawing a connection between work life and home life, only this time she's using rhyme to do it.
(part of the set), beside a big hirsute begonia.
The taboret is part of the wicker furniture set, because we know that you were just dying for that detail.
"Hirsute" means hairy or bushy. So this table with the comic books is beside a bushy begonia plant.
Begonias usually have very bright flowers. Here's a sign of life amongst all this grime! But why did our speaker tell us that the comic books were the "only note of color" in this scene? Maybe the begonias aren't in bloom? That's a bummer.