I'm an amateur who just started using Bumble Bee XB3. Can anybody please
tell me how you can obtain a color disparity heat map using the Visual C++
environment. Because by default the disparity map is in grey scale.

You can use the stereo_view utility in image_view to view the color-mapped disparity image. There's no public API for doing that mapping, but you can look at the stereo_view.cpp source code to see what we do.

Secondly do you recommend to use the factory default calibration or
calibrate the camera to your specified parameters in order to get a good
disparity image.

There have been a couple other threads on the mailing list about using the Bumble Bee XB3 if you search the archives. Someone was working on using the factory calibration to produce rectified images - unfortunately that's a bit difficult to integrate with the rest of the image_pipeline right now, though it will get easier in Diamondback. Another way is to just recalibrate using camera_calibration and let stereo_image_proc do all of the processing.

Cheers,
Patrick