WebPlus X6: Default Site Background

My default Master Page background colour has changed from white to an unwanted colour.

I have been through the process of Edit/Site Properties/Page Background to change the colour and then Tools/Save Default Options.

However, when I create a new site, it reverts to the unwanted colour.

I know I can change it manually, but would like to know if I can reset the default background to what I want.

I am able to set other defaults such as page size.

Many thanks