Normal metals are made up of millions of tiny crystals. If the metals are distorted / deformed the individual crystals distort slightly different depending on their individual orientation. Since the distortion of each individual crystal (grain) is non uniform the surface of the overall structure becomes slightly more rough. The more the metal is distorted the more roughness appears. Straightening the wire causes a lot of distortion of the grains. The grey color is a result of light not being reflected uniformly from the rough surface. This is normal and has absolutely nothing to do with the safety of the wire for vaping. Relax and enjoy.
Duane
Thanks for the quick reply...I was pretty sure it would be ok. Just wanted to make sure, after 52 years of smoking...didn't want to develop another bad habit.