Place red or white potatoes and sweet potatoes in 4-quart Dutch oven; add enough water just to cover potatoes. Cover and heat to boiling; reduce heat to low. Cook covered 20 to 25 minutes or until sweet potatoes are tender; remove sweet potatoes from Dutch oven. Cook red or white potatoes 10 to 15 minutes longer, if necessary, until tender. Drain potatoes. Let stand about 15 minutes or until cool enough to handle. Peel potatoes; cut into cubes.

Mix mayonnaise, milk, cumin seed, salt and chilies in large glass or plastic bowl. Add potatoes, bell pepper and onions; stir gently to coat. Cover and refrigerate at least 2 hours to blend flavors.