Even if you’ve been using Slack for a while, you might not know about the Sidebar Theme feature in Preferences, which is a good way to keep your different Teams visually separate.
Sweet Themes are Made of These is an unofficial resource for Slack sidebar themes. I actively participate in two different Slack rooms and I use the sidebar themes to keep them straight at a glance.
There’s a brief how-to if you don’t know how to change your Slack sidebar theme.
I’m using the light and dark Solarized themes and think they look great!