The difference is a lot more than color. The GH3's higher bit rate means that it can resolve more image detail in complex scenes (e.g., water, landscapes).
You can modify ("hack") the GH2 in order to record at a higher bit rate, but it's a lot of hassle.
I never bothered to hack my GH2 – it was a lot easier to simply upgrade to the GH3.
Also the GH2 has been discontinued – so it's almost impossible to find one that is still under warranty.
The GH3, on the other hand, is still available new, with the full manufacturer's warranty, for less than $800.
Good luck with your decision!
Bill
Hybrid Camera Revolution
