src/ccDarkTheme/components/_thread-insert.scss

// ec-thread-insert is a card with a summary of a thread when escalating it.
ec-thread-insert .title {
  color: var(--TWPT-primary-text)!important;
}

ec-thread-insert ec-thread-counts,
    ec-thread-insert .details,
    ec-thread-insert ec-relative-time {
  color: var(--TWPT-subtle-button-background)!important;
}