The Oz flag is a rectangle quartered diagonally, resulting in triangular colored fields in the four cardinal directions, or up, down, left, and right — reproducing the general geographic relationship of the four countries of Oz. In the center is the green symbol of the Emerald City. The Oz books, however, do not agree on the color scheme of this basic pattern or on the central symbol.
In Dorothy and the Wizard in Oz, chapter 17, the four colors in the fields are sky-blue, pink, lavender, and white. The cerullian shade matches the characteristic blue of the Munchkin Country, the lavender the purple of the Gillikin Country, and the pink the red of the Quadling Country; the white would have to correspond to the yellow of the Winkie Country. It sounds as though this first flag had been bleached of its vibrant colors, perhaps through long use. This flag has a green star at its center.
In The Magic of Oz, Chapter 5, the four countries of Oz are described as having their own banners in their dominant colors; the national flag has the four colors, blue, red, purple and yellow, plus a "green center," shaped unidentified. This form, consistent with the traditional colors of the four countries, is widely reproduced and generally regarded as standard.
The earliest picture of the Oz flag, rather than a verbal description, seems to have been released in connection with Glinda of Oz in 1920. On it, the central symbol is an eight-sided green emerald shape, with the letters O and Z intertwined in white at the center.
In Ruth Plumly Thompson's Captain Salt in Oz, the Captain flies "the green and white banner of Oz." This is not necessarily an inconsistency: naval vessels can fly a "jack flag" that features the portion of their national flag that signifies unity. (In an American example, the blue field with white stars on the national flag would constitute the jack flag.) Captain Salt is the "Royal Explorer of Oz," sailing on official business; it would be perfectly correct for him to fly a green-and-white jack flag of Oz.
The Featherheads of the Skyle of Un have their own flag: it is a bright yellow banner bearing the word UN. (The Cowardly Lion of Oz) The Blanks of Blankenburg have only a makeshift flag — a pink blanket. (The Lost King of Oz)
In The Magic Book of Oz, Scott Dickerson creates a flag for the Quadling Country, consisting of five red stripes of varying hues, and three white stars in an inverted triangle; and one for the Munchkin Country, which displays three bluebells against a field of periwinkle.
- Robert R. Pattrick. "The Flag of Oz." The Baum Bugle, Vol. 2 No. 2 (October 1958).