Hopefully useful description.
Full Hybrid vehicles combine functions of both series and parallel hybrid systems, and have the ability to move the vehicle with power from the IC engine, the electric motor, or a combination of both. The actual contribution from each power source depends on vehicle design and mode of operation. The engine can drive a generator to supply power to both the electric motor and the high voltage battery, or supply power to the drive wheels in conjunction with the electric motor.
The full hybrid has a motor/generator (MG1) attached directly to the engine, and a second motor/generator (MG2) attached directly to the drive wheels. The engine, MG1, and MG2 are interconnected through a compound planetary gear set. This allows the control module to direct power from the engine or both motor/generators as required. The 2007 Altima Hybrid is a full hybrid.
The reason why the tach does
The reason why the tach does not dip into the blue area on cold start while the engine is running is somewhat difficult to understand. When operating on a cold start, sitting at a red traffic light with your engine on, your battery is in fact charging, HOWEVER, the reason why the meter does not dip into the blue area is because this blue area only indicates how much energy you are regenerating through BRAKING, not by the engine. The lower the needle drops into the blue, the harder you are braking, thus the more energy you are recapturing during your braking. If your engine is running while stopped, it is in fact charging the battery. I hope this puts your curiosity to rest.