DI stands for Direct Ignition.
Red DI cassettes were used for DI, DI/APC and Trionic 5.
Black DI cassettes where used for Trionic 7.
Cars designed for red cassettes should not use black and vice versa. There are internal differences to the cassettes and it is not recommended that you use a red cassette for a car designed for a black cassette. Even though the car may start with a different DI cassette it may cause engine failure in the long run.
Don’t forget to replace the spark plugs when changing your DI cassette. Old spark plugs can often cause damage to a new DI cassette.