01
Assemble the adjacent materials
Place representative slate beside the proposed flashing or trim finish and relevant wall materials. Look at the combination outdoors. Ask the supplier or designer how the metal appearance is expected to change, and distinguish that discussion from confirmation of technical compatibility.
02
Record both selections together
A later change in metal finish can alter a combination that looked balanced during initial review. Keep a labeled sample record and have substitutions checked against it. Where existing metal will remain, include it in the comparison rather than expecting new components to look identical immediately. The goal is a coordinated roof whose stone and visible detailing have been considered as one composition.