Set the freezer control for fast freezing.
Pick mint leaves from the stems and chop.
Add the water and sugar to the chopped leaves and boil, stirring, until the sugar has dissolved.
Let stand and cool.
Add the corn syrup, lime rind and juice and enough coloring to give a delicate tint.
Pour into the freezing tray and freeze until firm.
Remove the mixture to a bowl and break up the lumps with a wooden spoon.
Beat until almost smooth but still a thick mush.
Fold in the beaten egg whites, return to the tray and freeze until firm.