Clothes-washing machines are going greener under an agreement unveiled yesterday between the U.S. government and major home appliance manufacturers. By 2007, Whirlpool, Maytag, General Electric, and other companies will make washing machines that use less water and 50 percent less energy than current models. More modest energy efficiency gains will be achieved by 2004. Manufacturers that exceed the efficiency standards in the agreement will get tax credits. Enviro groups said the changes will save consumers about $75 a year in energy costs, and Energy Secretary Bill Richardson said they “will save enough electricity to light 16 million U.S. homes for 25 years while cutting greenhouse gas emissions by an amount equal to that produced by 3 million cars every year.”