I understand that, but I would be more confussed with the liveries. Like are there still planes flying with the old United grey livery? Or the newer white/blue livery? Is there planes still flying in Northwest colors?

There's no planes flying the NW colors anymore. As far as United it looks like for some time there will be a combination of the old stealth, white top Blue bottom, and merge liveries. Continental seems to be rushing to put 'United' on the side of their planes where as United is moved slow as snails with their paints.

Dillon, It is not that Continental is more eager than United to paint their respective letters on their fuselages as United to paint their tails with Continental logos. It is a technical issue. The moving surfaces Ailerons, Elevators, Flaps and Rudders are subject to Flutter, so they need to be properly balanced. Changing the paint could affect the balance of the rudder, since the other parts are not painted they are not affected. If you noticed in pictures of brand new Boeings, Airbuses, DHC, EMB etc you can see that the rudder is the only part that is painted, (see attached) Here is a more technical explanation:Flutter can be induced by bumping the flight controls while operating at the upper end of the speed portion of the performance envelope. To prevent the possibility of Flutter, flight controls are kept as light as possible and are balanced. The balance can be both static and dynamic. This accomplished by the location of the axis of the hinge and installing weights inside the leading edge of the flight control. These weights can be made of a heavy material, such as lead or depleted uranium.The flight controls on some airplanes and certain controls on a particular airplane type are more sensitive to flutter than the same control on other types and so the limits of unbalance and even the requirement to balance a flight control may or may not be required depending on the aircraft type.If a control must be kept in balance, then anytime the control is repaired or painted, the additional weight and its moment arm must be calculated or checked on a balance table for its affect on the balance of that control.It is relatively easy to calculate the changes to a flight control balance due to a repair. But painting over existing paint or stripping and repainting will normally require removing the control and rebalancing on a balance table. Many paint facilities do not the equipment or personnel (A & P's) to accomplish such work, thus the requirement to leave the rudder alone as it is normally the only flight control that is painted.RegardsJuan