In The Pearl, how does the clothing of Kino and Juana contrast with the doctor’s?

You can find the answer to this in Chapter 1 when Kino and
Juana take their son with them to seek medical attention when he is stung by a scorpion.
What is key to realise is how Steinbeck uses the differences in the appearance of the
doctor and Kino and Juana to reinforce the sense of social injustice that pervades the
novel. Let us remember that, when Kino reaches the door of the doctor's house, he
hesitates, remembering that the doctor was not of his
race:

This
doctor was of a race which for nearly four hundred years had beaten and starved and
robbed and despised Kino's race, and frightened it too, so that the indigene came humbly
to the door.

This helps
explains Kino's reluctance but also his absolute dependence on the doctor. Let us
consider how they are described however. As they begin the procession to the town to see
the doctor, Kino and Juana are described by those that see
them:

And the
newcomers, particularly the beggars from the front of the church who were great experts
in financial analysis, looked quickly at Juana's old blue skirt, saw the tears in her
shawl, appraised the green ribbon on her braids, read the age of Kino's blanket
and the thousand washings of his clothes, and set them down as poverty people and went
along to see what kind of drama might
develop.

Note how the
emphasis is on the poverty and suffering that Kino and Juana have experienced, with the
"thousand washings" and the "tears in her shawl." Contrast this then with the
presentation of the doctor:

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He had on his dressing gown of red watered silk
that had come from Paris, a little tight over the chest now if it was buttoned. On his
lap was a silver tray with a silver chocolate pot and a tiny cup of eggshell china, so
delicate that it looked silly when he lifted it with his big
hand...

Clearly, with the
quality and material of the red gown highlighted and the physical possessions that are
emphasized, the doctor is from a very different background, as as Kino fears, abuses his
power by refusing to help them because they cannot pay.