dark: Dark as night, dark as midnight, etc.
black: Black as jet, black as midnight, etc.
What do you expect authors can compare to other things black?
Black as stone? Black as my keyboard? Black as my pencil sharpener? Black as sewer water?
Yes, but generally, aren't they portrayed as the color blue? Like I said above, what do you expect authors to compare blue with? Blue as a Winows XP toolbar? Blue as bed sheet? Think, dude. We might be creative but it's sometimes important to use your so-called "cliched similies."
Black as my battery charger. Black as the fence.