WASHINGTON — The first USS Colorado fought in the Civil War. The second patrolled the Pacific Ocean a century ago. The third, a battleship, bore witness to the end of World War II. On Saturday, the fourth USS Colorado began the namesake’s next chapter — this time as a $2.6 billion, nuclear-powered submarine. The U.S. Navy put the new boat into active service for the first time at a shipyard ceremony in Connecticut that brought together top military officials and Colorado politicos such as Gov.