Hey - sorry to re-open an old thread but I thought people might like to know that it looks like BMW have removed the restriction of only allowing Mineral White with the Pure Balance package on the Z4.
I was able to configure a Mineral White 2.0i M Sport with Walnut leather in the online configurator, took it to the dealer and it was accepted into the dealer's system with no problems.
Goes on the production line around 22nd April!!
Might be a world first ;-)