I’ve been using tabbed sessions in the ACS 5250 emulator for a long time now. I really like the tab feature; tabs along with watermarks made it easy to identify which system I am logged in to. With a bit of configuration, you can make it easy to identify the active tab as well as customize the appearance of inactive tabs.
The trick is knowing that there are two different places to do this configuration.
The tab appearance for active sessions is under Edit→ Preferences → Tab Setup. You can get to this from the 5250 session manager or the 5250 window itself. The screen capture below shows this menu option from the 5250 session.

Tab Setup… allows you to turn tabs on or off and control their placement, among other things.
Tab Setup… also allows you to configure the appearance of your active tabs. This is a global configuration, which makes sense because you can only have one active session at any time.
The screen capture below shows the configuration settings you can specify for the appearance of the active tab:

I like to have a bold color for my active tabs and have selected a black background with green foreground and a large courier new font.

In addition to configuring what the tab looks like for your active session, you can also configure what tabs look like for your inactive sessions. This is a configuration parameter for each session, which allows you to customize different inactive tab appearances for different systems. I have two IBM i partitions – dmi1 and dmi2 – and I want to easily distinguish between the two when I have inactive sessions.
I do this configuration by taking Edit → Preferences → Appearance → Tab Appearance, as the following screen capture shows:

I left the background as default, but changed the foreground color. I’ve configured different foreground colors for my different partitions so it’s easy to identify different systems.
You can see from the following screen capture that I have two sessions for two different partitions. It’s obvious which is the active one and easy to tell the difference between dmi1 and dmi2.

You may want to also read the IBM Support Technote IBM i Access Client Solutions 5250 Emulator Tabbed Sessions Configuration.
There are all sorts of customizations you can make to your individual 5250 session configuration for colors and fonts, watermarks, etc. You can also save those customizations as your default configuration. This is hidden under Communication → Set As Default Profile.

After you have saved your configuration as your default profile, new sessions will use the saved configuration.
This blog post was originally published on IBMSystemsMag.com and is reproduced here by permission of IBM Systems Media.