The egg white recipe is listed right above the sugar cookie recipe. Sorry it was not labled. I've included it below for your convenience.
"Egg White Paint is simple and quick to make. The paint requires no special materials. All that is needed is an egg white, water, food coloring, water color paint brush(es) and container(s). Simply mix the egg white with 1/4 teaspoon to 2 tablespoons water and mix. Divide the mixture into the number of containers needed for the colors you wish to create. (For younger children two colors will be sufficient.) Then add your (or your child's) choice of food coloring to each container. The paint is now ready for your child to paint on cookies or breadsticks with a water color paint brush for a colorful treat at the dinner table."
Also, for thicker paint consider adding cream of tartar. Or for a sweeter taste add a small amount of sugar.
Hope that helps.