Although the recipe calls for red radishes, you could use others of a similar shape and size. Also, after a day, the radishes lose their red rims and the entire radish turns a pale magenta. They lose the hot edge of a radish, and will smell a little like sauerkraut, but will not taste as strong. These quickles are not a subtle flavor, but they go well with things like braised beef, corned beef sandwiches, and are great with smoked salmon and especially herring pickled in white wine.