anti-red drabber?

Can someone recommend a drabber product/brand that will effectively reduce unwanted red tones in the hair? i would ideally like something that could be added to shampoos/conditioners, or that could be used as a rinse, outside of hair coloring. i recently had my hair colored, but the old red undertones are still there, and I'd like to get rid of them.I know there are products that will do this, but i dont know any names or brands, nor which are the most effective/least damaging to colored hair.thanks for any suggestions! :) silvie