Ok. If I have interpreted your post correctly you want to not use the default colors for values not defined in your theme (i.e. defaulting to transparency).
I see two options to combine to your theme:
- replacing any default colors using the command above
- using the transparency plugin so any colors not defined in your theme will be transparent
It's been a long time since I checked the config options but yt-fzf only supports mpv as media player I think.