Green’s Dictionary of Slang

(UK black) a black man or woman who is ‘black on the outside but white inside’.

1999		(con. 1979–80) A. Wheatle Brixton Rock (2004) 211: He’s a friggin bounty. I dunno what Jean sees in him.
2002		Guardian Rev. 30 Mar. 2: The insults ‘coconut’, ‘Bounty bar’ and their American equivalent ‘Oreo’ — all of which mean black on the outside and white on the inside.
2006		G. Malkani Londonstani (2007) 23: Din’t matter what you called them. Coconuts, Bounty bars, Oreo biscuits or any other food that was white on the inside.