N opened 1C. E overcalled 1S passed around to N, which doubled. That was passed out.
I led my singleton C6. When N got in with the SK, GIB led the C7 for my ruff. So, I returned my H5 - having read the C7 as suit preference for hearts. GIB should have led the C2, showing preference for diamonds.
Because GIB "knew" it might be giving me a ruff - or did it(?) - seems it would be an easy fix to incorporate its giving suit preference in this situation.