To keep my leafy vegetables fresh after I bring them home from the market, I soak them in a large tub filled with cold water and 1/3 cup of white vinegar*. After drying them with a salad spinner I loosely wrap them with paper towels and keep them in the refrigerator in a plastic bag.
I do the same with the herbs except after removing the lower leaves I put them in a jar filled with water and cover loosely with a plastic wrap just as in the picture (parsley). Removing the leaves below the water line will stop bacteria growth that promotes rut. They'll stay fresh two weeks without loosing their color or flavor.
* Another good use for vinegar. For more uses of vinegar you can click on