Welcome to Android Central! Which grayed out Google icon are you referring to? Google Search? You can go to the App Manager and disable as many Google apps as you can. Or you could root the device and remove Google apps, although you'd have to be cautious, because removing an app that is integral to the device's function might brick it.
No offense intended, but if you don't want to deal with Google, you may want to consider a different platform that isn't made by Google.