List scrollbar background pattern

Photon 1.13

I’m trying to create a scrollbar in a list widget that has an all white
background with black borders and colored thumb and arrows.

I use the ARG_LIST_SB_RES bit to set the scrollbar resources and can
successfully set everything the way I want except for the fill color (the
stuff behind the thumb). This area always has the scrollbars ARG_COLOR mixed
in with the ARG_FILL_COLOR via a pattern. I’ve tried setting the scrollbar’s
fill pattern to Pg_PAT_NONE with no joy.

Is this possible?