Cannot set default canvas color outside of Welcome dialog

Summary:

There is currently no way to set the default canvas color outside the Welcome dialog. One can hand-edit the preferences.xml file but it's not exactly ergonomic.

Steps to reproduce:

• open Inkscape
• open Preferences
• search for canvas color

What happened?

It's simply not there.

What should have happened?

It should be somewhere in the preferences.

Version info

Both 1.4 and master