yes they come in black as well as a wide array of other colors. They arent as common as say the millies and porcelains, but they do come in a dozen or so colors that are readily available and then another 15 or better rarer colors.
Where in other species like ducks, self just basically means a solid colored bird, self blue, self black, self chocolate....just duck terms for a solid color patterned bird.
The only "SELF" color in chickens is self blue, lavender, meaning they are a "blue" that breeds true basically. Some breed specific groups like the polish folks, like to add "self" infront of all their colors too, but techincally it's not a chicken thing. To me it's kinda like calling a dun bird chocolate, even though it's brown, it's not a "chocolate".