[Enhancement] Change tray icon (or color?) according to active input and output using custom icons/colors

[C-Duv]

Describe the enhancement

Ability to set indicator's tray icon according to currently active input and output.

Ultimately, setting the icon image from an user-provided icon would be nice, but keeping current one (indicator's logo) as a icon and only altering it's color could be OK for a start.

I think this would allow convenient and easy way to find out which input or output is active.

Expected behavior

From the settings window, for each input and output device I could set a custom icon (or color) that the indicator should display when said input or output is enabled.

Obviously, it needs to convey 2 information ("What is the current input?", "What is the current ouput?").

One way (simple ?) would be 2 icons/colors have to be displayed in the tray.

With custom icons

Here, user have set it's input to display it's webcam icon and it's output to display headphones:

or maybe display icons while keeping the original indicator's logo:

(I don't know what are the display possibilities of an indicator so I don't know what can be done)

With colors

Here, user have set it's input to display as red and it's output to display as blue (only he knows exactly what it means, it's his user taste/preference):