Does anyone know the diff between a Red Eibach C/T spring vs Dark Purple Eibach A/P spring?

I thought Eibach's were either red or black depending on the category. And I don't understand the "C/T" and "A/P". I've seen "Z/X" as well. Especially that those 2 springs are in the same ERS category and have the same part number except for the spring rate of course.
Google is pretty bad when using "/" as a search criterion.

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