File: public/js/tinymce/src/core/src/demo/css/content_editable.css

.mce-content-body *[contentEditable=true], .mce-content-body *[data-mce-contenteditable=true] {
  background: #adffad;
  border: 1px solid #999;
}

.mce-content-body *[contentEditable=false], .mce-content-body *[data-mce-contenteditable=false] {
  background: #ffadad;
  border: 1px solid #999;
  margin: 0 1px 0 2px;
}

.mce-content-body div[contentEditable=false], .mce-content-body p[contentEditable=false] {
  margin: 2px 0 2px 0;
}

.mce-content-body  *[contentEditable]:focus {
  outline: 2px dotted blue;
}

/* Debug overrides */

.mce-visual-caret {
  outline: 2px solid red;
}

.mce-visual-caret-before {
  outline: 2px solid green;
}

.mce-content-body *[data-mce-selected] {
  outline: 2px solid blue;
}

.mce-content-body .mce-offscreen-selection {
  left: auto;
  right: 0;
}

*[data-mce-caret] {
  outline: 1px solid green;
  position: absolute;
  left: auto;
  right: 0;
  top: 0;
  margin: 0;
  padding: 0;
}