Prepare 8x4x2 loaf pan with non stick spray, set aside.
Add the gelatin to the cold water and stir. Place this mixture in a double boiler and heat until the gelatin dissolves. Remove from heat and let it cool at room temperature.
Beat the egg whites until lightly stiff. Gradually add the sugar and salt one tablespoon at a time while mixing. Then add the cooled gelatin, almond extract and lime zest. Mix until well combined. Do not add hot gelatin to the egg whites.
Divide the egg whites into three separate bowls. Tint one bowl green and one red (the red will really be pink when mixed with egg whites). Fold the food coloring in and mix well to distribute the color evenly.
Using a tablespoon, layer the green egg whites in the bottom of a glass dish.
You can also use a mold if you like. Then add the white layer and last the red layer. Spreading the layers with the back of a spoon works well.
Cover the dish with plastic wrap and chill in the refrigerator at least 3 hours to overnight.
To serve invert pudding on a serving platter. Garnish with custard sauce if desired.