Black Fabric Dye To Cover Bleach. Be sure that the item is completely saturated. Black is one of the easiest fabrics to successfully remove bleach stains from.
Yes Machine Fabric Dye or Wash Dye are best for dyeing denim however you will lose the light dark contrast typically associated with denim. If the stain is light enough you might be able to camouflage it by coloring over it. This is a fast easy and cheap fix for faded or discolored spots.
But that isnt to say that you have to stick to black.
Well first of all with black and other dark colors you dont have to die the whole garment. Heat up the water over the stove until it reaches the temperature right before the boiling point. Fill it up with water allowing enough room at the top to prevent the water from spilling over in the dying process. It is not possible to dye a fabric white.