I haven't had the STAR in awhile, so I may be incorrect, but it is to my knowledge that
purple comes before maroon in air quality alerts. Purple means "very unhealthy" and maroon means "hazardous." Purple is not normally shown on the STAR unless it is needed, of course. I think the worst level I have seen on a STAR is red.
Also, I believe a Weather Bulletin for an air pollution watch is shown for levels orange and above, not just for maroon.
I am not sure if there is such as thing as a bulletin for an "air quality alert" though. (I assume there is a difference. To me, the alert is like a warning.)