[feature request] Allow alternating or cycling colors

[hrj]

In a complex function, the number of vertical lines can be high and a little hard to follow.

It would be great if two or more colors could be defined in the preferences, and the lines would be drawn with different colors for different indentation levels.

[hrj]

Here's a screenshot of what I have in mind:

The shades of grey are alternating.

[kiritsuku]

While a valid ticket report, I'm not going to work on this. I mainly maintain this project because the previous maintainer doesn't want to do it anymore. Because I don't have a need for this particular feature the chances are low that anything comes from my side for this one. But I'll happily merge a PR if someone want to work on this.