How do I Make Firefox Print a Background-Color Style?

Question

I have some simple CSS:

#someElement {
    background-color:black;
    color:white;
}

It looks ok in the browser, but when I go to print it

Answer 1

For chrome you can use this:

-webkit-print-color-adjust:exact;

Or in print preview, tick the More settings->Background Graphics

For Firefox, you can't enable it using any CSS. You can enable it as follow (If you don't see the File, press Alt key once).

File->Page setup and tick the Print Background(color & images)