Outlook for Web Arc Boost

outlook-web-boost.css

div[aria-label^="Unread "] span[title] {
  font-weight: 900 !important;
  color: #000 !important;
}
div[aria-label^="Unread "] div {
  background-color: #ff0 !important
}
div[aria-label*="Flagged"] div {
  background-color: #fcc !important
}
button[aria-label^="Go to today"] {
  background-color: #800 !important;
  color: #fff !important;
}

@media (prefers-color-scheme: dark) {
  div[aria-label^="Unread "] span[title] {
    color: #0fa !important;
  }
  div[aria-label^="Unread "] div {
  background-color: #000 !important
  }
  div[aria-label*="Flagged"] div {
    background-color: #fff !important
  }
}