Enum is a type with a restricted set of constants values. Here is an example, as follows:

pragma solidity ^0.4.24;
  contract ColorEnum {
    enum Color {RED,ORANGE,YELLOW, GREEN}
    Color color;
    function construct() public {
     color = Color.RED;
    }
    function setColor(uint _value) public {
      color = Color(_value);
    }
  function getColor() public view returns (uint){
      return uint(color);
  }
}