YOU MAY NOTICE this morning that Metro's own little elves have been through all the subway cars in the wee hours and put some new red trimming on the route maps. That's to confirm that, as of today, four new stations have joined the Metrorail network along the Red Line: White Flint, Twinbrook, Rockville and Shady Grove. And while the maiden voyagers are hopping aboard the trains with shopping bags ready to get a jump on motorists crawling through holiday traffic, a good word about some less visible but equally significant progress for the subway system: In addition to more Red Line, there is new

Green in the picture as never before.

Don't head for those tracks this morning, but do know that some important, delicate negotiating has been going on among the representatives of the various local governments at Metro to end four years of controversy over a key section of the Green Line. This week, the Metro board voted -- unanimously -- to build a six-mile section from Anacostia to a Prince George's County terminus near Branch Avenue. This clears the way for Metro officials to ask a federal judge next week to lift a court order that has blocked construction for nearly three years.

Of interest to District residents -- and a critical factor in this latest agreement -- is the routing of this Green Line section via Congress Heights in Southeast, with a Southern Avenue station at the D.C.- Prince George's line. This would mean improved transit service to St. Elizabeths Hospital, Greater Southeast Community Hospital and areas of employment in Prince George's, including a federal office complex at Suitland and Andrews Air Force Base.

So how does an agreement like this suddenly come about? If you look behind the scenes these days, you find a savvy negotiator in Metro General Manager Carmen Turner. You also find increasingly realistic and determined board members from all around the region seeking creative solutions. To resolve this Green Line/Congress Heights issue, for example, the District agreed to consider splitting with Prince George's the costs of building the Southern Avenue station. Some county and state officials had been pressing before for a cheaper route to Branch Avenue that would have excluded the Congress Heights or Southern Avenue stations.

It's called bargaining -- and coupled with one of the tightest Metro bus and rail annual budgets to be proposed, it is further strengthening the regional commitment to support completion of the full subway network initially agreed to by the White House, Capitol Hill, two states and every participating local government. In turn, this local commitment -- with a timetable that could save big money and deliver the promised service to all who have been paying up from the start -- is what the administration sought as a necessary part of this joint venture. Now the understanding of the White House and Congress is critical.