Themes can use color_scheme in the theme manifest to specify light/dark mode, otherwise they will use auto mode which is subject to change between versions. Currently auto mode uses the toolbar color to decide if a theme is considered light or dark.

firefox color scheme is already set to dark, I've tried automatic, played around with different combinations, that didn't change anything, and I've tried changing it in about:config, and everything in there is already set to dark..... I've reposted a few of my themes, hoping they would update back to dark, but that also didn't work. I've made no changes to my settings to cause this, it's always been in dark mode with no problems, and all of the sudden, a week ago(??), all the drop down menus went white, but toolbar and bookmarks menus are still dark.....i'm open to all suggestions

Themes override the browser's color scheme. You can directly edit the color_scheme in the theme manifest or adjust the toolbar color to trigger automatic dark mode.