Use of diamond icon for events in Activity graph is not straightforward

In the Activity page, we use diamond icons of different colors to signify events.
Purple is for Quality Gate
Blue is for Version
Grey is for Quality Profile

This is not straighforward at all, as users have to guess and remember what colors stand for. In this tooltip for example, it's nearly impossible to understand what's happening:

This is also not accessible to colorblind people (we should never use color as the only signifier or differentiator)