Editting CSS files

To change the colors of your Firefox you have to use userChrome.css. To modify the one provided here, the only thing you'd have to do is change the values of the variables at the top of the file (as far as you know some basic css or color coding, it shouldn't be too hard, since the variable names are descriptive of what they change) using notepad, or some code editing program (such as notepad++ on Windows).

For example, if you want to change the background color of the address bar to pure black, you could use either #000000 or rgb(0,0,0) inside the --lwt-toolbar-field-background-color variable:

*|*:root:-moz-lwtheme {
...
--lwt-toolbar-field-background-color: rgb(0,0,0) !important;
...
}

You can find a color picker to hex code in this page, or you can try to guess the color considering that for both hex and rgb format the first number (each 2 numbers in hex code) belongs to red, the next to green, and last to blue (thus why RGB).

You can also turn the features you want on or off changing the commented lines on any file (To change them you just have to open it with notepad or any code editor, and encase between /* and */ the lines you don't want to take effect). Of course, if you think that you are NEVER going to use certain feature, you can always delete the specific lines you don't want without any other side-effect.

For example, if we have this rule:

p {
  color: white;
}

If we want to comment it out, we would surround the whole thing with /* and */:

/*
p {
  color: white;
}
*/

If there are comments in between, we will have to comment out each part before and after the comment:

/*
p { */
  /* This changes the text color to white */
/*
  color: white;
}
*/

If you want to learn more about CSS, you should try with the Mozilla or the W3schools tutorials.