base.css

:root {
  --jp-execute-time-highlight: var(--jp-brand-color3, #bbdefb);
  --jp-execute-time-background: var(--jp-cell-editor-background);
}

/* Transition to highlight a cell change */
@keyframes executeHighlight {
  from {
    background-color: var(--jp-execute-time-highlight);
  }
  to {
    background-color: var(--jp-execute-time-background);
  }
}

.execute-time {
  background-color: var(--jp-execute-time-background);
  display: flex;
  justify-content: space-between;
  margin-top: 2px;
  font-family: var(--jp-code-font-family, monospace);
  font-size: 86%;
  border-top: 1px solid var(--jp-cell-editor-border-color, #cfcfcf);
  padding: 0 2px;
}

.execute-time.execute-time-contrast-low {
  color: var(--jp-ui-font-color3);
}

.execute-time.execute-time-contrast-high {
  color: var(--jp-ui-font-color1);
}

.execute-time.execute-time-positioning-left {
  flex-direction: row;
}

.execute-time.execute-time-positioning-right {
  flex-direction: row-reverse;
}

.execute-time.execute-time-positioning-hover {
  display: none;
}

.jp-Cell-inputWrapper:hover .execute-time.execute-time-positioning-hover {
  display: block;
  position: absolute;
  right: 0;
  bottom: -1.25em;
  border: 1px solid var(--jp-cell-editor-border-color, #cfcfcf);
  border-width: 0 1px 1px 1px;
  height: 1.25em;
  z-index: 3;
}

.execute-time.execute-time-hidden {
  display: none;
}