Put the dates and walnuts through a food grinder.
Add the vanilla; blend well.
Shape into 36 small balls.
Beat the egg whites with the salt until stiff.
Gradually add the sugar and continue beating until very stiff and glossy.
Divide the mixture in two parts; tint half with a few drops of green food coloring to obtain a delicate shade.
Repeat the process with red food coloring.
One by one dip the date-nut balls into the tinted meringue, using a teaspoon.
Place on a greased cookie sheet, swirling the tops of the meringue attractively.
Bake in a 250° oven for 30 minutes, or until the tops are delicately browned.