Is there any difference between the Warthog plane and the A-10 Thunderbolt in design etc. (except the color scheme)?

The A-10 Thunderbolt II is the same plane as the Warthog. Thunderbolt is it's official name. Warthog is what it's affectionately known as.

I once heard a rumour that the US airforce wanted to phase the A-10 out of service because they were losing a few due to pilots simply hitting the ground during training flight but the US army pressured them into keeping them as they are such good close support aircraft.

WHAT! Do you mean they want to face off those great crafts? They're pretty good in terms of tactical combat. With that great arsenal, it is really useful for tactical firing. Darn those pilots! Can't they utilize it's abilities?

The A10 was supposed to be replacede by newer versions of the A10.
You must remember that the A10 si getting a bit old now !
Also, it's survivability on a modern battleground is often placed in doubt (the same applies to helicopters).

Shonen : training of fighter or bomber pilots always costs a few planes and sadly a few lives. If you want to be efficient in combat, you must be able to push your plane "to the edge". And to do so, you must train, train hard. And sometimes someone pushes the plane too far, or there is a mechanical failure.