In their first appearance, we meet three old Munchkin men, who seem to be diminutive in stature:
They were not as big as the grown folk she had always been used to; but neither were they very small. In fact, they seemed about as tall as Dorothy, who was a well-grown child for her age, although they were, so far as looks go, many years older.
Three were men and ... were oddly dressed. They wore round hats that rose to a small point a foot above their heads, with little bells around the brims that tinkled sweetly as they moved. The hats of the men were blue... The men were dressed in blue, of the same shade as their hats, and wore well-polished boots with a deep roll of blue at the tops.
Personally, I stick with the color of clothing, decor and flora.
The Munchkins appear to be be mainly farmers, though there are also woodmen and at least one tinsmith among them, as well as the quirky countries Ruth Plumly Thompson introduced.
W.W. Denslow drew all the Munchkins as diminutive people, and then he appears to draw all the other people of Oz at about the same height. When John R. Neill took over as illustrator, there was more variance in height in Oz. However, he didn't draw the Munchkins until The Patchwork Girl of Oz when he presents Ojo and Unc Nunkie as normal-sized people. I personally prefer this look of diversity for Oz. Perhaps the first ones that Dorothy met were very short, but not all of the Munchkins are that short.
Of course, when the MGM film created their Munchkins, they based their look partly on the Dainty China Country and had all of the Munchkins played by little people and a few children. These diminutive Munchkins were so charming that "Munchkin" has become slang for little people or children. Similarly sized Munchkins have made their way into Disney's Return to Oz and Oz the Great and Powerful.
Still, I prefer the idea that Munchkins could be three feet high or six feet high. The only thing that makes them Munchkins is that they live in the east part of Oz.
The Munchkins have different names as well. The names we were given by Baum were Boq, Nimee Amee, Ojo, Unc Nunkie, Bini Aru and Kiki Aru.