Stir the peach gelatin mix with boiling water in a bowl to dissolve the gelatin. Allow to cool to room temperature, about 20 minutes. Mix in the evaporated milk and peach schnapps; pour into the prepared mold. Refrigerate until set, 4 to 6 hours.
To decorate, dip the mold in very warm water (don't let the water enter the top of the mold) to loosen; invert the mold on a serving platter and lift to leave the brain in place. Mix blue and red food coloring in a small bowl with 2 teaspoons of water. Use a small clean paintbrush to paint the coloring into the grooves of the brain. Return the brain to the refrigerator until the food coloring sets. Serve cold.
