message: art: Changement de couleur du bouton d'explication
  Les actions ont cette couleur
diff: text-align: center;
  width: 1.3em;
  line-height: 1.3em;
  - border-radius: .2em;
  + border-radius: 0.2em;
  display: inline-block;
  - margin-left: .4em;
  - padding: .15em;
  - opacity: .4;
  + margin-left: 0.4em;
  + padding: 0.15em;
  + opacity: 0.65;
  border: 1px solid transparent;
  border-radius: 1em;
  cursor: pointer;
  vertical-align: baseline;
  font-size: 95%;
  + color: #2975D1;
  }
  .explicable .icon:hover {
  */
  .explicable.explained .icon {
  opacity: 1;
  - background: #4A89DC;
  + background: #4a89dc;
  color: white;
  }
  