Q: Why FCP X change my video color?

I can't really see what your problem is?

Part of the clip in the Browser looks dark the same as the Viewer.

Did the lights go out when you were shooting that bit?

Is the clip in the Browser dark?

Need more precise info.

Very strange. Is it the same when you drag the clip to the storyline ?

I suggest you try the old fashioned remedy we use when something strange happens that we can't explain.

Try trashing the preferences with this app 

http://www.digitalrebellion.com/prefman/

You have to download it and follow the instructions.

Please give the complete specs of your computer system including the video card.

It seems that you card is not supported but to be sure check here http://support.apple.com/kb/HT4664

I checked again it is not supported The following graphics cards are not OpenCL compatible and do not meet the OpenCL compatible graphics card system requirement for Final Cut Pro X, Motion 5, and Compressor 4. Intel GMA X3100

No version of FCPX, but there is no other than 10.0.3 available, sad to say