I tried to dye batting for some Christmas pillows in red, green, gold and white. It worked but I can never wash the pillows because I will never feel comfortable about washing out all the left over dye. If there is even just a smidgen left in the batting it will bleed all over the outer quilted fabric. This means my beautiful pillows are dated as far as their life span is concerned. I worked really hard on the applique, embroidery and quilting to ever try to dye batting again, EVER.
I will just buy black batting from now on. Hancock's carries the black as well as white and neutral.