how do i dye clothes black stardew without wasting hours?

Also check the item is actually dyeable. Some shirts and pants just aren't, and the machine will take the coal and do nothing. The item description says if it can be dyed.

nothing's been patched, you're just on the harder of the two methods. sewing machine at emily's - clothing in one slot, something black in the other. coal does it, squid ink does it. one pass often isn't enough if you started from a bright colour, so keep feeding it back through. the dye pots next to the machine work too, but you have to get an item into all six pots before the menu will let you pull the value slider down to black.