After updating Firefox to version 145, the New Private Window background has changed. I’d like to customize or revert this background to what it supposed to be in the past (a much darker color which, in my opinion, much easier for the eyes). Below is the newer version:
Firefox-specific sites use this CSS for background:
:root {
background-color: var(--background-color-canvas);
}
the variable is defined for various pages, including the private window one, which marks its html with private class:
@media not (prefers-contrast) {
html.private {
--background-color-canvas: #25003e;
}
}
To change it, simply override the variable with own color, with !important if needed. Use userChrome.css modifications for this purpose. Instructions differ per system which you haven't provided, see this answer for Windows ones.