I am no expert on screws. When I go buy some, I'm typically handed screws that have a silvery color. I have never asked about the metal composition. Still, occasionally I notice you can also get sets of black/dark-gray colored screws, like these:
and that they're intended for use with drywall.
I'm assuming the color is not just a coat, and that they're indeed made from some other amalgam/material than your typical silvery screws. Are they also (significantly) weaker, for a given diameter? e.g. do their heads break off more easily? Does cam-out remove more of their material than regular screws?
Black Drywall screws AKA sheetrock screws, gypsum board, sheetrock, plasterboard & general purpose screws
Black Drywall screws can be used as all purpose screws or wood screws: good for medium duty wood screw use. If used as an all purpose wood screw, use for interior application. Black/Gray phosphate coating. Black Drywall screws are a great low cost solution to everyday, non-structural wood screw applications
Different Sizes 6 mm x 1″