Temporary files show a white-on-grey "temporary" badge:

The code tries to make this badge yellow:

$ttl = $file->getTTL();
if ($ttl !== null) {
  $ttl_tag = id(new PHUITagView())
    ->setType(PHUITagView::TYPE_STATE)
    ->setBackgroundColor(PHUITagView::COLOR_YELLOW)
    ->setName(pht('Temporary'));
  $header->addTag($ttl_tag);
}

@chad, I can probably fix this if you don't have any insight, but wasn't sure if maybe there's some bigger issue here like "yellow is no longer supported and we should remove the constant" or "yellow is supposed to work".