Just a little more info.
--you have to factor in the cost of the plastic &
--factor in the cost of paying whomever is going to mold these with an injection molding machine--it will be cheaper to make 2000,5000 or 10,000 units in one production run(or until the aluminum mold wears out..).It will not be economical if you only make 500 cart cases at a time--the molding company will charge you for every time you have to set-up your mold into their machine.
--As far a the different colors go--make the clear ones first,then put the diff. colors in; after the colors are switched(without stoping the machine), you would get weird combinations of colors in between diff. lots of colored plastic, but it looks cool.(besides, you will not be able to afford to throw them out anyway.)If you want to make clear parts again, after making colored ones, you have to clean the screw/barrel on the plastic injection machine-or once again you could just add clear and have a milky not so clear product for a while.
--the bottom line is time=money good luck with this project...