I know of only 2 versions of a blonde Ozma. One is in the 1980s Disney "Return to Oz" movie where little Ozma is blonde (in order to differentiate her from Dorothy IMO) and the other is in the original illustrations of the first time Ozma appears (after she changes from Tip) in "The Marvelous Land of Oz". After that O'Neil, the primary Oz illustrator, started to draw her as a brunette (with the flowers on the side of her ears and her "OZ" tiara) and visibly a few years older than Dorothy (especially after she and Dorothy became best pals).
Following "The Wizard of Oz" - the 1st book - in which Dorothy was a brunette (like Judy Garland), Dorothy has always been depicted as a blonde and that continues in all non-movie versions of the stories still today.