Green’s Dictionary of Slang

piebald adj.

1. (Aus.) using blacks and whites as fellow-workers.

[Aus]Bulletin (Sydney) 10 Aug. 18: Thing first is leaving the country because Australia isn’t piebald & won’t let him employ black slavery on his sugar plantation.

2. (Aus.) half-caste, mixed-race.

[Aus]Bulletin (Sydney) 17 Aug. 13/1: For some years a white barber has battled along [...], displaying a placard to the effect that his business has no connection with the adjoining shops of Chows, Bashi-Bazouks, etc., who gradually ousted his white neighbors. Passed the place recently, and noticed that the piebald alien had at last slopped over into the barber’s shop.
[Aus]Bulletin (Sydney) 22 Sept. 11/4: By the way, the binghies in this district all more or less speak Malay, and blacks and Malays are intermarried (another piebald-Australian problem).
[US](con. early 1950s) J. Peacock Valhalla 347: Butch and the piebald Negro looked on anxiously.

In compounds

piebald pony (n.)

(Aus.) a mixed-race white/Aboriginal child.

[UK]E. Hill Territory 445: Piebald pony: A half-caste child.