About.com recommends removing a tomato sauce stain by running cold water through the stain, rubbing a liquid detergent, applying a mild bleaching agent, and using a stain remover stick. If your stain is a combination of two or more stains, such as an oily spaghetti sauce, get rid of the oily part first by using mild dish detergent.
The first step is to remove any excess tomato sauce from the fabric by using a spoon or the back of a butter knife, states About.com. Next, run cold water through the back of the stain, and then rub a liquid detergent into the stained area. Rub the fabric in gentle, circular motions starting on the outside region of the stained area. For white garments or those that have been tested for colorfastness, use a sponge to apply a mild bleaching agent, such as white vinegar, hydrogen peroxide and lemon juice. Wash the fabric thoroughly afterward.
Clean the stain again with detergent, followed by the mild bleaching agent, until the stain disappears, says About.com. Check that it is completely gone by holding the stain up to the light. Apply a stain remover gel, stick or spray, and leave it for around 5 minutes. Wash it again with detergent. If the stain remains, rub detergent into the fabric again, and soak the clothing in warm water for half an hour. Rinse it thoroughly afterward.