There is some cross model confusion hapenning here- hopefully this will help.
There are two systems of immobiliser used- Bosch Code 1 - Alfa 145/6 and GTV/Spider and
Code 2 - Alfa 147/156 and 166
There is a transponder inside the key of both systems which operates the immobiliser by radio signal transmitted from the immobiliser to the transponder and verified each starting sequence.
If the car has remote central locking, each key will also have a transmitter inside with a battery- this is totally separate to the transponder and immobiliser system.
The difference comes in the key ordering and programming sequences.
Code 1 keys are supplied as blanks which need to be cut and programmed into the immobiliser. This is done with the (BROWN) master key which has a special transponder embedded in it and unlocks the immobiliser to enable programming or deletion of keys.
This key is vitally important as it is necessary to program and delete keys, there is no access to programming of this system through the diagnostic computer. If the master is lost it is not possible to program further genuine keys into the system. If all keys are lost- the engine management and immobiliser computers will need replacement along with keys and barrels. If you do not have the central locking code from the code card the receiver will also need to be replaced.
If like Richard your car has remote central locking and you have no code, buy a new receiver and get it programmed, they aren't that expensive as a part and you can then program the existing keys to a new code quite simply.
It is however possible with this system to clone any of the existing keys if you find a locksmith who has the appropriate machine to copy and duplicate the transponder. This will only work with non genuine keys.
Code 2 is more complicated and secure. This uses a rolling code transmitted into the transponder. There is no master key, all keys are the same (the other key in a 166 is just a valet key) This system requires the keys to be ordered by chassis number from the factory by the dealer- no blanks are available.
With this system no master key is required as the programming is done via the diagnostic computer. All keys on the Code 2 cars can be lost and replaced- there could be some delay obtaining them depending on where you live!
Replacement keys can only be programmed in by a dealer with the appropriate computer and code card- as supplied from the factory the keys will not start or open the car. Any keys not present during the programming procedure will be deleted permanently and cannot ever be used again.
As far as I am aware these keys cannot be cloned but are produced to order as necessary by the factory. I can't understand how a black key could be supplied instead of a red one unless it was ordered under an incorrect chassis number- the lock barrels and central locking receiver are totally different.
In Australia the immobilser programming code is supplied with all new cars- the central locking code must be ordered from the factory- usually with the key. If the code card is lost a new one can be ordered from the factory. I have also heard that this is not supplied with the car in the UK for insurance and security reasons- your dealer should be able to confirm this.
Hope this helps