discourse/app/assets/stylesheets/common/select-kit/user-row.scss

.user-chooser {
  .select-kit-row.user-row {
    .avatar {
      margin-left: 0;
      margin-right: 0.5em;
    }

    .username {
      color: $primary;
      white-space: nowrap;
    }

    .name {
      color: $primary-high;
      font-size: $font-down-1;
      margin-left: 0.5em;
      overflow: hidden;
      white-space: nowrap;
      text-overflow: ellipsis;
    }
  }
}