GnuCash 3 Black Theme

gtk-3.0.css

/* 
  GnuCash 3.0 black theme 
  GTK has a way of declaring variables, which is not a valid CSS anymore and
  tooling support is gone.
  CSS has a way of declaring variables, which is not supported by GTK.
*/

* {
  background-color: black;
  color: lightsteelblue;
}

/*
Examples of other selectors:

window {}
window label {}
box * {}
*/

/* This is an example using CSS variables but it does not work with GTK3.
:root {
  --main-bg-color: black;
  --main-fg-color: lightsteelblue;
} 
window {
  background-color: var(--main-bg-color);
  color: var(--main-fg-color);
}
*/
/*
Example of using GTX variables:

@define-color bg_color #f9a039;

* {
  background-color: @bg_color;
}
*/

On Windows, this goes into C:\Users\<user>\AppData\Roaming\GnuCash