CAD tip # 12326:

You cannot add your own custom styles but you can customize settings of any of the existing predefined styles. The style settings are stored in XML files and the background color hue is set through the key Background (except for the style "Photo Booth"). XML files for the individual environments are stored in the subfolder Neutron\Server\Scene\Resources\Environments in the Fusion 360 production folder, e.g. (single line name):

c:\Users\USERNAME\AppData\Local\Autodesk \webdeploy\production\79ccc336d91fd2d46ed87a5b819b04c15b878e83 \Neutron\Server\Scene\Resources\Environments\DarkSky\DarkSky.xml

(you can locate this folder e.g. over the INI file in the Target folder at the Fusion 360 start icon on your desktop)

Open the XML file with Notepad or in another text editor and edit the RGB values of the Background key:

In the Fusion 360 environment, switch to the environment you have modified (in our example: "Dark Sky"):