Use a small serrated knife to cut 1½ inches from the pointed end of the sugar cone. Discard the tip.2.
Line 2 cookie sheets with wax paper. Break the potato chips in half lengthwise by holding each long side and snapping them (they will be irregular).3.
Microwave the green candy melts and the vegetable shortening in a medium bowl, stirring every 10 seconds, until completely melted and smooth.4.
Dip a potato chip into the melted candy to cover (see photo). Allow the excess candy to drip back into the bowl. Transfer the chip to one of the cookie sheets. Repeat with the remaining chips, reheating the candy for several seconds if it becomes too thick. Refrigerate the coated chips until the candy is set, about 5 minutes.5.
Spoon the remaining melted candy into a Ziplock bag; do not seal the bag. Reheat the candy in the microwave, massaging the bag every 5 seconds, until smooth. Press out the excess air and seal the bag.6.
Snip a small (1/8-inch) corner from the bag. Place the cut cone, wide opening down, on the second cookie sheet. Cut a 12-inch piece of aluminum foil and fold it in half lengthwise. Gently crumple the foil and shape it into a ring around the base of the cone (this is the support for the first row of green chips). Pipe some melted candy around the base of the cone. Attach a row of green chips, pointing upward, rounded edge against the cone, using the foil to support the chips (see photo). Transfer to the refrigerator to set, about 5 minutes. Continue adding rows of green chips up the side of the cone, reheating the candy, as necessary, and chilling after each row, to cover the cone. Arrange 3 chips upright in the top opening of the cone. Refrigerate until ready to use. Reserve any extra leaves for the platter.7.
Place the loaf cake on a work surface. Trim ¼ inch from each short end with a serrated knife to make straight. Stand the cake on one cut end and cut a ½-inch bevel on all four corners to round the shoulders of the cake. Transfer the cake, in its upright position, to a serving platter and place in the freezer for 30 minutes to chill.8.
Tint the vanilla frosting yellow with the food coloring. Fit a large Ziplock bag with the star decorating tip, if using. Hold the bag inside out in your open hand and, using a spatula, spread half of the yellow frosting in a thick line up one side of the bag. Spread half of the chocolate frosting in a thick line up the opposite side of the bag. Bring the sides of the bag up and over the frosting. Press out the excess air and seal the bag.9.
Starting at the bottom, pipe a row of 1-inch stars, very close together, around the base of the cake. Repeat, piping additional rows of the frosting. As you pipe, the colors marbleize in the star; turn the bag every few stars to vary the design. When the bag is empty, repeat with a clean Ziplock bag and the remaining yellow and chocolate frostings, washing the star tip, if using, and continue to cover the cake completely, including the top.10.
Transfer the pineapple crown to the top of the cake, gently pressing it into the frosting to secure. Arrange any remaining leaves on the serving platter.