What colours can the Bella Cantata bloom in Streetpass Garden

If you run out of HP, you basically "quit" — it will end your session, and take you back to the title page, and you won't get to use any other Miis or the like that you collected that day. Every session starts with full HP.

In my experience, you get rating opportunities if one of the following three things occur:

1. The second time you meet someone.
2. When you meet someone you've met before and they've changed their hat.
3. An unknown criteria when you meet someone past the max number of times (currently 999). This one seems to have a pattern (maybe every 10?) but I don't know what it is.