Hi Jaime,
If you want linear color, the right approach is to generate and assign an ICC profile for your display, and then make sure that MWorks’ color management support is enabled (in the advanced display preference window that your mentioned). To generate the profile, you’ll need a calibrator (something like this.) For more info, please see this discussion. (There’s another explanation here.)
The display gamma settings are an inferior method of linearizing the display, as I noted in the first linked discussion. But if you want to go that route, you need to determine your display’s gamma values in the red, green, and blue channels and enter them in the preferences window. MWorks will then instruct the OS to apply the inverse of those gamma values to the display, thereby canceling out the display’s inherent nonlinearity.
I’m not sure how you should measure your display’s gamma values. You could use a calibrator like the one I mentioned (the gamma curves are part of the generated ICC profile), but if you’re going to do that, you may as well just use my recommended approach.
I hope that helps!
Cheers,
Chris