Is there a way to apply color coding to the iPad calendar provided by Apple ?

Not from the iPad itself. If you sync the calendar with the Mac then some of the colours applied there appear to 'come across' (if I sound unsure, it's because I'm a PC user and I'm trying to recall posts that have been around on this topic).

If you want to do this directly on the iPad then the best way forward is to use a third-party calendar app that 'sits on top of' the native calendar. I use Pocket Informant HD which has a plethora of features - too many to mention but you can download the User manual from the Developer's web site - but it most certainly allows you to apply colours.

Tim