Banana jack colour schemes

Banana jack colour codes used by modular synth brands for which some reference has been found. Note that there is no universal accepted standard.

Considerations
In the UK Rapid only sell 4mm bannana sockets in black, red, white, green, blue and yellow.

There isn't always a clear distinction between audio and control signals. It's more important to distinguish between inputs and outputs. There might be some unusual connections such as inputs with restrictions and ground for external patching.

Patch cords are color coded to indicate their length.

Buchla 200e
On Buchla synthesizers the audio and contol paths and control are kept seperate. The control path uses EF Johnson banana jacks and swings between +/-15V, while the audio path is at 1.228V RMS, (+4dBu professional line level) and uses 0.141" Tini-Jax.

BugBrand
Most modular synth signals can be thought of as either audio or control. The system ground jack provides a ground for connecting to external systems with screened (3.5 mm or 1/4") jacks, so that the signal can be carried with single wire cables (white in Bugbrand interface packs).

Front panel
Regards audio and control signals as interchangeable.

Castle Rocktronics
Tries to have a different colours for each different type of input, although just one colour for all outputs.

Serge
The Serge scheme is more about the type signal than its function. With some flexibility e.g. some CVs can go negative. Many black inputs are AC coupled, but most black outputs are not.