firefox-gui-chrome-css/chrome/userContent.css

// input, textarea, select { color: #000000; background: #ffffff; -moz-appearance: none; }
// input[type=button], input[type=submit] { -moz-appearance: button; }
// input[type=checkbox] { -moz-appearance: checkbox; }
// input[type=radio] { -moz-appearance: radio; }