Not sure what you mean. Is the Studio User Interface white? Or is the Viewport and Ground Plane of your scene white? If the latter then the problem is that the UI layout changes, so telling you how to fix it requires we know what version of Daz you're using. But in general, Googling "How to change your background colour in Daz Studio 4.7" will give you an idea of how the fix used to be done. It's a complex process.

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Learn the Secrets of Poser 11 and Line-art Filters.