Has anyone out there ever heard of a BROWN filler for hair and if so what would it be used to correct? I know you use red to correct for BLOND going to BROWN and neutral to keep porous ends from becoming to dark.

Hair color fillers are available in most colors, even brown. It's basically used to rebuild the hair pigment lost due from bleaching or sun damage. Once the hair filler is applied, then the desired color is apply over the filler to produce long lasting results. You may find these at your local beauty supply store.