Top bar/browser colors to prevent uploading files to the wrong client

[stefpix-oss]

I use Cyberduck professionally to upload photos to several different clients, often with multiple FTP/SFTP connections open at the same time.

It would be very useful to assign a color to each bookmark/connection and have that color remain clearly visible while connected — for example as a colored strip, tab color, toolbar accent, or other persistent visual cue.

The main reason is to prevent uploading files to the wrong client. For example:

Newspaper A = red
Magazine B = blue
Agency C = green

For people working with competing clients, accidentally uploading the wrong photos to the wrong server could be a serious and embarrassing mistake. An accidental upload could easily happen under a tight deadline, especially when working under stress, pressure, or sleep deprivation.

A persistent color cue would provide an immediate visual check before uploading.

Even something simple, like a narrow colored bar at the top of the browser window inherited from the bookmark, would be very helpful. Ideally, the bookmark/connection name could also remain prominently visible alongside the color.

This seems technically quite feasible. Cyberduck already stores per-bookmark information, so the main work would likely be adding a user-selectable color and carrying that into the browser UI. A simple colored strip or tinted header should be relatively low complexity compared with changes to transfer functionality itself. The main challenge would probably be keeping the implementation visually consistent across macOS and Windows.

This would be less about customization and more about reducing human error when managing multiple client connections.

[dkocher]

Relates to #9719.