Rumour is the black DI is a retrofit so can be used in older Trionic cars and the red DI cannot be used on later cars. if true, this would be consistent with SAAB's philosophy of updating new parts to replace and supercede older parts on older cars.
I do know that the platinum plugs specified to be used in the newer 9 5 (which uses the black DI) also work with the red DI in the older cars.
The 9 5 initially used the red DI but later models moved up to the black one.
There was an old old black DI in 1990 or 1991. Don't use that in any newer cars, it was designed for the first HO turbos using the 2.0 liter engine.