I did a simple prototype locally using hsl(hash(tag) % 360, 100%, 40%), the above trace would become like this

Why do you need to distinguish them? What are you trying to glean from the ticks & colors?

Let's say the span is a coroutine that polls events from other coroutines, and the tag is the name of the source coroutine or the type of event.

Alternatively, the ability to distinguish logs by level (error/info) would be useful too.

Are you interested in submitting a PR to implement this?

Regarding the UI experience, I would do it this way:

• Add a Settings icon ⚙️ at the end of the header (to the right from Archive Trace button)
• In the popup dialog have an entry 'Color log ticks by: [tag]'
• Have that setting persisted in local storage so that it's sticky for the user

Sure. I am not sure if we want to persist it in local storage though; how would that interact with multiple tabs opened concurrently?

Why would that be a problem? If user changes the setting, already opened tabs would not change, but if they are reloaded then they will reflect the setting.