It seems like most of us 3200GT owners dont bother about having all the keys, code cards, etc.
Maybe I can at least give you some information about the 3200GTs security system:
The 3200GT has two completely different security systems:
(1) The remote System is made by "Meta System" (Italy) and consists of the remote fobs in the black keys (the red key doesnt have a remote), the alarm control unit and the red code card with a 16 digit hex code.
You can add new remote fobs to your car, but only if they were precoded with the code from the red card. So if you loose the red code card you can't add new remotes.
(2) The immobilizer system made by Magneti Marelli.
Everytime you turn the ignition on with a working key the Immobilizer Unit sends the unique masterkey (which is also stored in the red key) to the engine ecu (only then the engine ecu will let you start the engine).
"Working Key" means that its transponder key is stored in the Immobilizer Control Unit, it also doesn't matter if you use a red key or black key.
The only difference is, that when using the red key, the immobilizer unit activates a key storing mode with which you can store more black keys within a timewindow of some seconds.
The grey Code Card contains a mechanical key (for cutting the keys) and an electronic code which is (lets say) part of the whole masterkey.
With the electronic code you can start the car by "typing" in this key with the accelerator pedal, f.e. if your black keys dont work anymore and you dont have a red key.
In contrast, the electronic code on the grey code card is not enough information to make a new red key (as it doesnt contain the whole masterkey).
If you loose your red key and your immobilizer control unit doesnt work anymore or you loose both black keys you will have to buy a whole set of new keys and control units which is very expensive.
So I would say its very important to have the red key.
Of course its also nice to have if you want to sell your car
Hope I could help you with that.
Cheers,
Carl