In a small bowl, dissolve orange gelatin in 1-1/2 cups boiling water. Pour into an 8-in. square dish coated with cooking spray. Refrigerate until set. Repeat with lime gelatin and raspberry gelatin, placing each in a separate 8-in. square dish.
In a saucepan, combine unflavored gelatin and cold water; let stand for 1 minute. Add lemon juice. Heat over low heat, stirring until gelatin is dissolved. Remove from the heat; cool.
In a bowl, combine the graham cracker crumbs and sugar; stir in butter. Reserve 1/2 cup for topping. Press remaining crumb mixture into a 13-in. x 9-in. dish coated with cooking spray; set aside.
Cut the orange, lime and raspberry gelatins into 1-in. cubes. In a large bowl, beat cream until stiff. Fold in unflavored gelatin mixture, then fold in flavored gelatin cubes. Transfer to prepared dish. Sprinkle with reserved crumb mixture. Cover and refrigerate for 2 hours or until set.