hints.css

.CodeMirror-hints, .cm-tooltip.cm-tooltip {
  position: absolute;
  z-index: 10;
  overflow: hidden;
  list-style: none;

  margin: 0;
  padding: 2px;

  -webkit-box-shadow: 2px 3px 5px rgba(0,0,0,.2);
  -moz-box-shadow: 2px 3px 5px rgba(0,0,0,.2);
  box-shadow: 2px 3px 5px rgba(0,0,0,.2);
  border-radius: 3px;
  border: 1px solid silver;

  background-color: white;
  font-size: 90%;
  font-family: monospace;

  max-height: 20em;
  overflow-y: auto;

  tab-size:  3;
}

.CodeMirror-hint, .cm-tooltip li {
  margin: 0;
  padding: 0 4px;
  border-radius: 2px;
  white-space: pre;
  color: black;
  cursor: pointer;
}

li.CodeMirror-hint-active, .cm-tooltip li[aria-selected] {
  background-color: #08f;
  color: white;
}