Issue with covers in Edit metadata in bulk

[spiceyhot]

I create covers for my fan-fiction library using calibre generate default cover. I use two different colors for my books one for complete and one for incomplete. Now I might be wrong but I swear that it allowed me to pick which cover I wanted when I clicked the generate default cover button when editing metadata in bulk. Now when I click the button I don't see a way to choose what color I want and it just chooses randomly.