slack.css

.light_theme .message {
  color: #fff;
  font-size: 16px;
}
 
.message .mention {
  //background: #ccc;
  //color: #f60;
  font-weight: bold;
}
 
.member_preview_link {
  display: none;
}

#channel-list li.channel {
    display: none;
}

#channel-list li.channel.unread {
    display: block
}

#channel-list li.channel.mention a{
    color: yellow !important;
}

.chanel .no_just_unreads.channels_list_holder .unread_just {
    display: block;
}

a.channel-list-more {
    display: none;
}