Artificially colored oranges received in bulk and sold at a retail establishment are not required to bear a label statement declaring the use of artificial coloring, provided the oranges are displayed to the purchaser.
Historically it has been the policy of the Food and Drug Administration to allow the artificial coloring of the skins of mature oranges. It is a common practice to color the skins of oranges in certain orange growing areas of the country because of climatic or cultural conditions which cause the oranges to mature while still green in color. The coloring of the skins of oranges is done in one of two ways:
Per the link