tanjq87, the quick and lazy (but time-consuming) way is to shoot RAW and fix WB later.
The more tedious way is to make use of the Auto mode, which resets everything each time you use it.
Flourescent light
flickers and so it's better you use a fast shutter speed and rely on the flash to light indoors. If not you get a greenish cast which is not consistent unless the shutter speed is slow enough.
Try 18mm F3.5 ISO3200 with drive mode set to burst mode. Fire away in a flourescent-lit room. See what happens?
Anyway, you can then set your camera to M mode with flash, with the WB set for tungsten light (anywhere between 2500-3200K). Now, turn to Auto. Notice how it changes to AWB? Now, turn to M. Notice how it remembers the WB setting earlier!
So that's one quick way to switch between two "profiles".
Alternatively, you could use a tungsten gel, and shoot in flourescent light at tungsten WB (but at a fast shutter speed and dark aperture to kill the flouro flicker) while using tungsten WB for tungsten light also. This doesn't require any switching modes.
thanks for your reply, looks like if i dun use flash, the best way is still AWB..
so sometimes if the colours were too saturated, is it because of wrong white balance?