table.css

/**
 * Allow users to specify the background color in all themes.
 *
 * (Users can set this using CKEditor 5's optional TableProperties and
 * TableCellProperties plugins.)
 */
.ck tr,
.ck th,
.ck td {
  background-color: transparent;
}

File

core/modules/ckeditor5/css/table.css

/**
 * Allow users to specify the background color in all themes.
 *
 * (Users can set this using CKEditor 5's optional TableProperties and
 * TableCellProperties plugins.)
 */
.ck tr,
.ck th,
.ck td {
  background-color: transparent;
}