You didn't mention what is changing... Only thing I can see is the brightness of the texture. If that's the case, it's likely the environment. The lighting probably changing from file to file resulting in the differing color. Another thing could be the gamma settings of the KeyShot file. What about Image Styles, are you using a Photographic Image Style? Unfortunately, there's a lot that could cause such a change. Without two files to compare, I really couldn't pinpoint the issue. Hope this leads to a discovery.