The 'Blues' who keep the nation's Capitol safe are seeing green. 

The officers who patrol the metal detectors and corridors of the Capitol Hill complex are earning some of the best pay and benefits in the business. A new government report shows the U.S. Capitol Police, or USCP, provides top-shelf pay when officers sign up and top-shelf benefits when they retire. 

Though the union is pushing for further improvements, the Government Accountability Office noted that so far, those officers are making out all right. 

Starting salary for the cops on the Capitol steps? Just about $56,000. 

And talk about benefits. Officers can retire at age 50 provided they've worked at least 20 years. Those who work for 25 years can make, on average, about $39,000 a year in retirement pay, not counting Social Security and money from a 401(k)-style plan that federal workers have. 

"These enhanced benefits allow their officers to retire early and accrue retirement pensions faster than other federal police forces," the report said. 

The GAO compared Capitol Police benefits with those of nine other federal forces. The only other force with starting pay at the same level is the Supreme Court Police. 

The rest -- including Secret Service Uniformed Division and Pentagon Police -- have lower starting salaries. The lowest, for the National Institutes of Health Police, is about $39,000. 

The USCP pay is well above the starting salary for a member of the Washington, D.C., city police force -- that paycheck is $48,716. And the USCP starting pay is more than twice what recent college graduates have been earning lately. A Rutgers study last year found college grads entering the workforce in 2009 and 2010 were earning a median starting salary of $27,000. 

Part of the reason the Capitol Police have higher pay may be because the force has what the report described as a "wider variety of duties" than other federal agencies. Officers protect members of Congress but also patrol the congressional buildings and parkland. They handle traffic duties and respond to suspicious packages, and they provide protective service for lawmakers' family members.

The force has investigative duties but generally defers to the city's Metropolitan Police Department for the very serious offenses. According to an MPD document, Capitol Police handles criminal investigations on Capitol grounds, except in the case of homicides and serious sex offenses -- those are taken over by the MPD, with Capitol Police assisting. 

The GAO report was prepared after the police union floated several proposals for improving the benefits system. The Capitol Police Labor Committee proposed condensing the pay scale and raising the mandatory retirement age. 

Under current policy, the police force requires officers in most cases to retire at 57. The union wants to raise that to 60 so some officers can work longer if they wish. 

The GAO said that would have a "minimal impact" on costs while increasing the officers' retirement. But the Office of Personnel Management called the move "unnecessary," saying the officers' healthy benefits make retirement at 57 "economically feasible." 

Labor Committee Chairman Jim Konczos said his group was "dismayed" by that finding. 

"We were very shocked that OPM came back and said that it wasn't necessary," he said. 

He said the union will continue to push for raising the mandatory age, and changing up the pay scale so rank-and-file officers get bigger raises faster.