Ok, so yeah, non of the default coloraturas schemes have an impact.
What I did notice is that if I remove the DB panel then add it again by dragging to an edge so that it fills top to bottom, as opposed to the smaller panel in the side bar, if I then slowly remove it from its 'snapped' position the background color changes briefly from its default white to a dark blue background, thus revealing the listed db connections. Unfortunately and unexpectedly during that brief manouevre the background color returns to white again and the db connections become 'invisible' again.
If the panel background can be stabilised to a darker color or the db connection icons can be darkened, we are back in business.