Base16 for the cmus theme format. Relies on your terminal colors also being the same so make sure to use this in conjuction with base16-xresources or base16-iterm2 or whatever is the right template for the terminal emulator you have.
Cmus color display is a little borked, so the terminal colors from 8-15 aren't actually taken from the terminal color pallete, they are just bold/brighter (depending on terminal emulator) versions of 0-7. You can see the relevant source code here. This doesn't affect any of the themes here because they only use terminal colors up to 7 (you don't need that many different colors for the UI of a music program).
Since this template only uses the first 16 ANSI colors, it doesn't even need to be generated. You can grab default.mustache and use it as your permanent cmus theme. It will always adapt to your terminal colors, whether they were generated from base16 or not.
Put into ~/.config/cmus.