'Jaffa cake' was the livery of the London & South East Sector of British Rail before it became Network South East. Therefore, the Network South East colours effectively superseded it. There is another thread ongoing talking about the possibility of blue and green based versions of the orange stripe livery that didn't happen -
https://www.railforums.co.uk/threads/l-se-green-livery.278475/.
It was carried by many of the large fleet of class 411 (4-CEP) units, but also by some class 309 units and a handful of class 421 (4-CIG) units.
The small number of 4-CIG units didn't carry Jaffa Cake livery for very long, and neither did the 309s, being repainted into NSE colours quite quickly. There were a small number of refurbished phase 1 CIGs that got blue-grey on refurbishment instead of Jaffa Cake as they were being refurbished right at the time Network South East was about to launch.
Information here about the 4-CIGs.
https://www.bloodandcustard.com/BR-4CIG.html
Information here about the 4-CEPs here
https://www.bloodandcustard.com/BR-4BEP-4CEP.html
The last repaint of a 4-CEP out of Jaffa Cake livery was in 1991.