Firefox dark theme workaround (https://bugzilla.mozilla.org/show_bug.cgi?id=519763) Inspired by https://wiki.archlinux.org/index.php/Firefox#Unreadable_input_fields_with_dark_GTK.2B_themes. Add it to ~/.mozilla/firefox/xxxxxxxx.default/chrome/userContent.css or using https://addons.mozilla.org/en-US/firefox/addon/stylish/ add-on. add-on.

userContent.css

input:not(.tactile-searchbox-input):not(.urlbar-input):not(.textbox-input):not(.form-control):not([type='checkbox']) {
    -moz-appearance: none !important;
    background-color: white;
    color: black;
}

#downloads-indicator-counter {
    color: white;
}

textarea {
    -moz-appearance: none !important;
    background-color: white;
    color: black;
}

select {
    -moz-appearance: none !important;
    background-color: white;
    color: black;
}