How to get mustard stains out of garments. (1)

Take the piece of clothing with stain and keep the stained area under running cold water. Then pour lots of dishliquid or a bar of soap and rub over the stained area. The soap removes the proteins in the mustard and will fight the discoloration. Leave overnight and wash as usual.
When you take it out of the washing machine first check if all stains is removed. If not repeat the procedure.