Vacuum up the boxelder bugs. Crushing them under your feet will leave stains. A vacuum will lift the bugs away without leaving traces behind.
Spray the bugs with liquid soap or laundry detergent. Do this away from any fabrics or materials inside the house that may stain.
Spray the bugs with an insecticide. You can use bifenthrin, cyfluthrin or permethrin. Be careful when applying these in the home. Make sure you follow the manufacturer's directions.