I have built some shelves that I specifically want to use black screws and washers for. Finding black metal washers was nearly impossible so I used some metal spray paint to make black ones. That works fine, but I cant really imagine doing the same with screws since a screw driver is going to be twisting them and probably stripping a lot of the paint off. I know roughly what kind of screws I need (3" length #8 screws with tight threading for drywall toggle bolts) but I cant seem to find any variation that are black. I was told mcmaster.com has a lot of options, but I couldnt use their filters to find anything specifically matching my needs.
There are black or dark-bronze screws available. If you can't find them locally check woodworking suppliers, or fastener specialists like McFeely.
There are also compounds sold for darkening/blackening metal. Again the woodworking shops are a good source; "gun blueing" might also work.
Better place to ask this sort of question would be on Woodworking.stackexchange.com.
I've done it with wood screws, multiple times, and it has held up fine. I screwed them into an old piece of wood to hold them and then sprayed them with 2-3 thin coats. No paint came off when using them. I used a manual screwdriver and proper pilot holes, not a drill or impact driver of course.
The screws were robertson head. I wouldn't advise it with philips head screws but it might just work anyway. Torx or flathead (with great care not to slip) would probably be ok.