For a new layout, you can choose the default theme on the theme panel to get a plain white background.
To change a layout part's color: Enter layout mode. Click the part label, (found on the lefthand side of your screen says "header", "body", etc.) and select a fill color just like you would select the fill color for any other layout object.
Did you try standard? Sorry I dont follow what the issue is. You can remove parts, fields etc, or you can start with nothing on a layout as well...