I hate to be the bearer of bad news of tomato stains are almost impossible to remove. Even using the Stain Devil removers, traces are often still left. You can try soaking overnight in water which has liquid Ariel or some other washing agent in it, but you may find that even prolonged soaking is not fully effective. The best protection again tomato stains on clothing is a very large pinafore or bib !
I know it's not quite the same but the trick for tomato sauce on clothes is simply holding the stain under cold running water and rubbing the stain between your fingers. Then apply a pre wash treatment and wash. Check the lable for washing instructions first though. Good luck!