To make broken glass Jello cake, first prepare a package each of lime, orange and strawberry Jello separately. Pour the Jello packets into separate 9-inch square dishes and add 1 cup of boiling water and 1 cup of cold water to each dish. Refrigerate for 4 hours until set.
While the Jello chills, heat 1 cup of pineapple juice in a saucepan until steaming hot. Do not allow it to simmer. Add a packet of unflavored gelatin and stir it until combined. Refrigerate the pineapple mixture for 30 minutes until it thickens.
In a separate bowl, combine 2 1/2 cups of graham cracker crumbs, 1/2 cup of melted butter and 1/2 cup of brown sugar. Set aside 1 cup of the resulting crumbs to use as a garnish. Line a 9 inch by 13 inch cake pan with the remaining crumb mixture.
Whip 2 cups of cold heavy cream until it forms light peaks. Combine the whipped heavy cream, 1/2 cup of white sugar and 1 teaspoon of vanilla extract in a bowl. Set this aside.
Remove the Jello from the refrigerator and cut it into cubes. Fold the whipped cream, the gelatin cubes and the thickened pineapple gelatin together, working carefully. Spoon the mixture into the cake pan and top it with the reserved crumb mixture. Refrigerate 3 hours or overnight and serve cold.