Mustard sauce is a great accompaniment for hot dogs, potato salad, and other dishes, but it does not suit wool rugs. The natural color of the mustard seed ranges from yellow to dark brown, and it was the first condiment ever used by humans. The ancient Greeks and Romans used their seeds as a cure for soothing aches and pains, an appetite stimulant, and to ease toothaches. A guide has been put together on how to get mustard stain out of the rug, following the handy steps.