Green’s Dictionary of Slang

(S.Afr.) the Cinderella Prison in Boksburg.

1948		in H. Tracey Lalela Zulu 54: They caught him and handcuffed him! / They sent him to ‘Blue Sky’.
1950		Drum (Johannesburg) Sept. 15: I did a nine-month stretch at the Cinderella prison (Blue Sky) in Boksburg [DSAE].
1979		E. Pahad ‘Yusuf Dadoo: A Proud History of Struggle’ African Communist , No.78, 3rd Quarter 🌐 Dadoo vividly recalls his prison experience at the notorious ‘Blue Sky’ prison in Boksburg.
1987		(con. 1950s) G. Moloi My Life 164: There was Godfrey Moloi on the road again [...] with chains on his wrists and ankles joined to scores of fellow prisoners, this time to Cinderella Prison (‘Blue Sky’) in Boksburg.
2003		(con. 1952) ‘Tribute to Walter Sisulu’ on S. Afr. Missions in N.Y. 🌐 Word seemed to have reached the inmates of ‘Blue Sky’ prison in Boksburg about the Defiance Campaign, so that when they arrived at the prison, the inmates gave the congress volunteers a rousing reception.