I sent a question about it to CZ-USA the reply appears to support what various other rifle owners mentioned:
"....The barrels are coated in a preservative grease prior to leaving the factory and are also blued(which is a type of rust) which can lead to that discoloration on the barrel surface from those two things.
A few patches should remove enough from the barrel to safely fire as long as they come out dry, but some residue will remain in pores for a while, which is normal and should not cause any safety, functional, or accuracy issues.
If you have any further questions or concerns please let us know and we will do our best to assist you.
Thank you,
Randal Stroud
Technical Support/Gunsmith Rifle Supervisor
CZ-USA
1-800-955-4486 x4706