It turns out that in the CSS file "classic.css" for the Window List extension, the taskbar text for a focused window button is specified as "white", which contrasts poorly with a light grey background. Changing "white" to "black" seems to work well. The attached patch was diff'd against the "classic.css" file from the Xenial Xerius Ubuntu GNOME live DVD for 4/9/2016.
It turns out that in the CSS file "classic.css" for the Window List extension, the taskbar text for a focused window button is specified as "white", which contrasts poorly with a light grey background. Changing "white" to "black" seems to work well. The attached patch was diff'd against the "classic.css" file from the Xenial Xerius Ubuntu GNOME live DVD for 4/9/2016.