How do I change/paint the color of a closet door floor guide
You are probably right, spray painting is not a long term option. But if you can't find this piece manufactured in black, spray painting might be your only option. That being said, I would make sure you prime it first (just google spray paint primer) followed by a couple thin coats of black paint. Over time the inside "tracks" will probably wear down, but you shouldn't see much of the inside once the doors are installed. The outside facing bracket should hold up fairly well, though. Sorry I'm not coming up with a better solution, but sometimes it just helps to talk through your project. Good luck!