options.icon.theme.pcss.css

.field-icon-selection_list {
  background-image: url(../../../misc/icons/55565b/selection_list.svg);
}

File

core/modules/options/css/options.icon.theme.pcss.css

.field-icon-selection_list {
  background-image: url(../../../misc/icons/55565b/selection_list.svg);
}