It is associated with joy, sunshine, and tropics.  Orange represents enthusiasm, fascination, happiness, creativity, determination, attraction, success, encouragement, and stimulation.  To the human eyes, orange is seen as a very hot color, so it gives the sensation of heat.
West Virginia, Ohio, Illinois, and Indiana form the northern border  of Kentucky, along the Ohio River.
Two of this country's greatest waterways, the Mississippi River on the state's eastern border, and the Missouri River, which winds across the state, helped Missouri become a supply center for many of the westward-bound settlers of the nation's early years.