discourse/plugins/chat/assets/stylesheets/common/chat-thread-header-buttons.scss

@mixin chat-channel-header-button {
  color: var(--primary-low-mid);
  padding: 0.25em 0.4em;

  .d-icon {
    color: inherit;
  }

  &:visited {
    color: var(--primary-low-mid);
  }

  &:hover {
    color: var(--primary-medium);
    background: var(--primary-very-low);
    border-radius: 5px;

    &:hover {
      .d-icon {
        color: inherit;
      }
    }
  }

  > * {
    pointer-events: none;
  }
}

.chat-channel {
  .chat-threads-list-button {
    @include chat-channel-header-button;
    position: relative;
    display: flex;
    align-items: center;

    &.has-unreads {
      color: var(--tertiary-med-or-tertiary);
      gap: 0.25rem;

      &:hover {
        color: var(--tertiary-hover);
      }
    }

    .d-icon {
      margin-right: 0;
    }

    &:hover {
      .discourse-touch & {
        background: none !important;
      }
    }

    &:active {
      .discourse-touch & {
        background: var(--secondary-very-high) !important;
      }
    }
  }

  .open-drawer-btn {
    @include chat-channel-header-button;
  }
}