I made a custom frame environment with dark background and white foreground. Unfortunately itemize overlays stopped working for such combination, only marker for currently highlighted item changes it's appearance.
Is there some variable that controls how overlay alters text in given environment?
I looked around the web and the questions are either how to change behaviour of one item or how to control sequence of actions. I also tried Beamer user guide but without success.
I didn't set \usebeamercolor[bg] so it was probably still white. When \setbeamercovered is set to transparent it uses a blend of bg and fg colors, so with white bg it stayed white.
Found in Beamer user guide 17.6 Transparency effects