Xfce 4.16 - Contrast problem in view-as-list version of "Alt-Tab"

[robertopierpaoli]

Hi, when using the vertical list version for "Alt-Tab" in Xfce 4.16 the selected item is marked in plain black over dark grey, which is a very slight highlighting, quite difficult to be seen (at least for me, on my monitors).
How can I alter the style sheets to gain a more contrasted rendering?
Thanks in advance and congrats for the amazing work.