Previously, fish would highlight the currently selected autocomplete. Now it doesn't. Do you know how to make it highlight it?
Expected behavior
The selected background color is stored in $fish_pager_color_selected_background, or $fish_color_search_match if that isn't set.
It seems either these aren't set, or the value you chose looks like your terminal's background. Given that you now have a light background and fish has no way to detect it that's hard to avoid.
Use something like
set -g fish_pager_color_selected_background --background=533
to set it. The value should look like arguments to fish's set_color builtin.
See https://fishshell.com/docs/current/interactive.html#pager-color-variables for more information.