[FEATURE] Visible marker for mix groups

[jatinchowdhury18]

Is your feature request related to a problem? Please describe.
Difficult to tell at a glance which mix group a plugin is in.

Describe the solution you'd like
Either a colour marker, or custom names for mix groups.

Additional context
From KVR user @sinkmusic:

One little thing : with mix group able plugins, I tend to like a hint a color to remember quickly which instances are linked.
So maybe adding a small color line above the bottom section (or being able to give a name to the group, ie "drums" instead of "2", or a little circle shape filled with a color next to the group number) could help identify quickly the groups ?

[jatinchowdhury18]

Currently implementing a small circle visualizer to accompany the mix group display: