Created attachment 6908 Preferences dialog (Colors tab) Setting a custom color for "Text selection color" only allows setting the background color of selected text. Foreground will *always* be rendered completely black, forcing the user not to select a dark color for the selection. See attached screenshot image for details. Since this was possible in xfce4-terminal prior to switching to GTK3, I consider this a regression.
Looks like vte3 requires separate settings for foreground and background colors. Will add them. Thanks for the report!
Fixed by https://git.xfce.org/apps/xfce4-terminal/commit/?id=7ffd8bad1e4b6b1daadbe664f48c869d61fcca15