There is a difference in monitor power management between Linux & Xp.
My monitor display gets off after 10 or 15 idle minutes with Linux(RedHat-9).But the LED of monitor remains Green.

With Xp i adjusted it to 1 minute.The LED of monitor goes to Orange color.

Monitor (ViewSonic E-43) manual says ...
Green LED -- Power mode (Working).
Orange LED- Power save mode.

Now my doubts...
1.Why is this difference in this regard? Is Linux really getting the monitor down or simply projecting black display?
2.What ever it may be how can I program the time interval to 1 min?

Please respond.

Your linux is projecting a black display. Regarding making changes, there should be a control panel which lists power management where you can make those changes.