My version is 20 14,
In the menu → File (or tool) → Options → Jump out of the dialog box (see above), Display → Under the window element, click the color button (that is, the blue button I selected), jump out of the dialog box (see below) → Select the position of 2D model space in the context, and select the position of viewport or unified background in the interface element. Set the color on the right.
If it really doesn't work, there is a button in the middle of the right to restore the traditional color.
I just restored the traditional color, and I don't want to change it when I get used to it.