X and Fluxbox :: how to set background color

Im using 4.4.10 and love it, but when using vnc since v3.* the background property does not persist after reboot so i just get a crosshatch.

Looking at the code, i cannot work out how to set the background color using a command that i could just throw in to ~/.vnc/xstartup

any help on say Black, or even an image?

xsri --color=black # solid black
xsri --color=black --color2=gray # gradient
xsri --set /path/to/image # set an image
xsri --help # more options, such as scaling and overlaying images


original here.