Pentosin 7.1 vs 11

["Dave C." <conner@cfm.ohio-state.edu>]

I've always used Pentosin 7.1 (green) in the 89 and 87 100/5k...audi PN
G002 000 
Now I've been dumping it in the 91 200tq (leaking hyd. pump).  I ordered
some for use in this car and the parts guy (not an Audi dealer) tells me I
should be using Pentosin 11 (red) in this car and the two must NOT be
mixed.  The label on the can of Pentosin 7.1 says not to mix it with Pent. 11

The sticker on the reservoir says use Audi PN G002 000.  My owners manual
says use Audi PN G002 000

I don't know for sure what's already in the system but was assuming it's
the green stuff.

So ...
Should I continue using the green stuff in the 91?
Is it a problem if the two are mixed?
Does the red stuff have a different Audi P/N?

Dave C.
Columbus, OH
91 200Q 20v avant 
89 100E
87 5KS 
86 4KQ