Cream butter and sugar together with an electric mixer for about 5 minutes until light and fluffy.
Prepare egg replacer in a separate bowl.
Add egg replacer and vanilla to creamed butter mixture and stir to combine.
Add flour and salt to butter mixture and stir to combine.
Divide dough into 3 equal sections.
Make a well in one section and add one to two drops of yellow food coloring. Knead dough until coloring is evenly distributed. Set aside.
Make a well in the second section of dough and add a drop of yellow food coloring and a drop of red food coloring. Knead dough until coloring is evenly distributed. Set aside.
Note that the third section is not colored with food coloring.
Spray a 9 x 5 inch bread loaf pan with cooking spray.
Press dough into the loaf pan in layers in the following order: plain, orange, yellow.
Cover and chill for 2 hours in the refrigerator.
Preheat oven to 350 degrees F.
Turn dough out onto a work surface.
Slice dough in ⅜ inch thick slices (as if you were slicing bread.)
Lay each slice on its side and cut into triangles (see picture.)
Bake cookies on a parchment-lined baking sheet for 7-9 minutes. Note that the cookies will continue to set after they are removed from the oven and should not be brown when you take them out.
Allow cookies to cool completely.
To make frosting, combine confectioners' sugar with 1 teaspoon of water. If necessary, add small amounts of water or confectioners' sugar until the mixture is a thick glaze.
Dip tips of cookies in the glaze, scraping excess off of the bottom of the cookie.
Allow glaze to set before serving.