Whisk egg yolks and sugar in a medium bowl until pale in colour then set aside.
Heat cream and milk in a large saucepan until simmering then remove from heat.
Slowly pour a cup of the milk into the yolks while whisking as quickly as possible. Then pour yolks back into the saucepan of milk.
Continue heating mixture on a medium heat until it thickens and coats the back of a spoon then remove from heat.
Stir in lime juice, salt, and food colour and refrigerate for at least 2 hours.
Churn ice cream as per ice cream maker manufacturer's instructions. As the ice cream begins to harden add the zest of lime.
Once churning is complete, scoop ice cream into an airtight container and freeze for 2 hours or until hardened.