Adding salt to the cooking water not only seasons your green beans and other cooked green vegetables but also helps them retain their bright color. When the green vegetables cook in unsalted water, some of the chlorophyll molecules lose their color-enhancing magnesium atoms; this causes the vegetables to turn a dull olive green. Salt stabilizes the chlorophyll, helping the vegetables stay greener. To maximize color retention without oversalting, use 1½ teaspoons of table salt for every quart of water.