How can i show my "green" light status in orkut even when i m logged in? ?

After you log in, in the home page, below your image and name, there is an "availability" option. When you click on that different options come - 'online' / 'offline' / 'idle' etc. You can select whichever. Depending on that the "availability" icon also changes - green / orange or some other. The 'green' light means 'online'. So, obviously it will be so when you are logged in.