Oranges color orange under the influence of cold temperatures. In the tropics the fruit keeps a green to green with yellow stains color. Choose oranges that are firm and heavy for size. Blood Oranges may have a full-colored blush or have no blush at all. Avoid blemishes and shriveled or moldy spots. For the juiciest, sweetest fruit, look for oranges with a sweet, clean fragrance. You can store oranges at cool room temperature for one week or for two weeks in the refrigerator