Rolling forward https://codereview.chromium.org/1155683008/ which was

third_party/polymer/v1_0/components-chromium/paper-radio-button/paper-radio-button.css

 /*
 Copyright (c) 2015 The Polymer Project Authors. All rights reserved.
 This code may only be used under the BSD style license found at http://polymer.github.io/LICENSE.txt
 The complete set of authors may be found at http://polymer.github.io/AUTHORS.txt
 The complete set of contributors may be found at http://polymer.github.io/CONTRIBUTORS.txt
 Code distributed by Google as part of the polymer project is also
 subject to an additional IP rights grant found at http://polymer.github.io/PATENTS.txt
 */
 
 :host {
@@ skipping 89 matching lines @@
 
 :host([disabled][checked]) #onRadio {
   background-color: var(--paper-radio-button-unchecked-color);
   opacity: 0.5;
 }
 
 :host([disabled]) #radioLabel {
   /* slightly darker than the button, so that it's readable */
   opacity: 0.65;
 }