Use seperate grey icon for the page action This does not stand out so much as the orange icon espeacially when using dark themes and should be readable on any theme since there is no transparency. Currently there is neither a way for addons to specify themed icons for page actions nor is it possible to use the browser's foreground and background color as native page action icons do.

/*
 * Copyright (C) 2018 Guido Berhoerster <guido+feed-preview@berhoerster.name>
 *
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/.
 */

@import url("common.css");

html,
body {
  padding: 4px;
}