rowntree's chocolate crisp was renamed kit kat chocolate crisp in 1937. the colour scheme and first flavour variation to the brand came in 1942, owing to world war ii, when food shortages prompted an alteration in the recipe. the flavour of kit kat was changed to dark chocolate; the packaging abandoned its chocolate crisp title, and was coloured blue. after the war the name became kit kat, with the original milk chocolate recipe and red packaging.