How to edit borders, colors and fonts of Inset forms with placeholder?

1

I am looking to remove borders, and possibly edit the font, font color and space colors for the inset list. Do I have to tweak it manually in CSS? If yes, how?

Referring to this page:

2

use !important in css

3

Using !important in CSS did not work for me, e.g. with this rule:

input:-moz-placeholder {
color: red !important;
}

The placeholder did not change colors to red and remained gray.

Has anybody been able to change the placeholder’s appearance (color)? Thanks very much for any pointers!