Linux

You probably already know, but scheme artists avoid pure #000000 out of contrast concerns. (e.g. DarkReader can give some headaches if the background is straight black with offwhite text). That makes a #000000 scheme very rare - manual intervention required :P

If you still wanna get crackin', just tweak a preexisting dark theme and change navies/greys to black. And if you're talking about the palette instead of actual themes to install, this still works -- just check the source for whatever colors they're using and tweak those. (grep for hexes then sort uniq? shell exercise is left to the reader)

I'd recommend taking one of vinceliuice's themes and just turning navy blues into blacks. For example, Graphite-gtk (has a matching qt theme) is pretty grey even with a --black tweak, but you could blacken it with some effort. Same with Colloid-gtk (also has a --black tweak).

You could probably even blackify the KDE theme's greys if you so fancied, but then you'd need to tune down the contrast on the other colors in the set. And this and that...

If this is too inexact an answer, then ouch. I wish you luck!

Do a web search for 'color pallet' and pick one that looks good with your black replacing the darkest color

If you're talking desktop/windows manager themes,

Graphite and colloid are a couple of my favorites.

It is offers customization via cli for things like borders, icons, compact/hdpi, etc.

The guy makes some pretty awesome themes

https://github.com/vinceliuice?tab=repositories

Theme for what?

You could use my GTK theme and tune the background color: https://github.com/He4eT/Desolate-GTK

Terminals usually allow you to choose any colors you like. For example you could pick any colorscheme here and tune the background color: https://terminal.love

Flexoki GTK theme

https://github.com/kepano/flexoki/tree/main/gtk

I ended up setting up custom themes for multiple different widget sets to get a true black background. It was easy for most QT variants, not too bad for GTK2, really awful for GTK3 because it doesn't have proper documentation for manual theme creation, and I haven't tried to tackle GTK4 yet.

Because they all need different configs (and the window manager title bar etc. may need yet another one), it's difficult to give suggestions unless you tell us which terminal and window manager software you're trying to theme—the requirements for a Gnome session are different from those for something like fluxbox. Some terminal software even has its own built-in theming support.