Different batches used for access route - defect?

If you have lost weight, then the burden of proof simply reverses ... which shouldn't really be a problem here now .... That means YOU now have to prove that the defect exists instead of the craftsman having to prove that it does not exist ... Set a deadline for defect correction. If that does not help, however, it becomes more difficult, especially if you have already paid.

To me, this looks like more than just two "batches"; I rather suspect the "same" color "similar to RAL xyz" from two different manufacturers or at least from two different plants. Have your lawyer explain to you which formal and deadline requirements your intervention should observe. This already starts with when it should be called a "notice of defects" or a "complaint." You are responsible yourself for the consultation of a lawyer. The assessment of an expert does not help here; if necessary, access to delivery notes would be required. Could it be that the construction company was both developer and builder here, and you are actually only the buyer?

Those are different stones. So one looks gray, the other anthracite.

Spoiler alert: Anthracite (colored) concrete stones do not remain anthracite. Over time, they always tend toward gray.

Time difference between the "batches"? Or was it laid at the same time? Are there delivery notes for the material? Do you still have outstanding payments or would you have to take legal action?