Piggin Red Keys LOL !
Every blue key has a unique ID which cannot be changed. The ECU keeps a list of the IDs which are allowed to start the ignition. The Red Key resets the list and is used to add or remove the ID of a blue key.
SO if you lose a blue key you buy a new one from Fiat (some dealerships apparently will sell you one uncut and you get the metal cut at a locksmiths to save cost) and use the Red Key to add it to the list, at the same time removing the lost one, so the lost key will open the doors but NOT start the ignition.
If you take a key to timpsons to get it done they will make a duplicate INCLUDING the ID, so if you take your Red Key you are getting another Red Key with an identical ID irrespective of what colour plastic it has on it. This means that if you lose it you cannot delete it, and every time you do use it it is resetting the list.
There are rumours that this constant resetting can cause ECU problems - RUMOURS...
My thought is that if you have the Red Key then do it properly and get a key from Fiat. Yes they may want £80 for one with a remote, but timpsons want £20 for the key with no remote, and then a replacement copy remote will be another £30.