Denver does not have a color system; if I understand it right, the alerts in Denver are based solely on weather conditions. That is, an alert is issued based on the potential for high levels of ozone and not the actual levels themselves.
Doing a little more research, I also found out ground level ozone is the principal ingredient in smog, so if we want to know the level of ozone in the air, we just have to look at how hazy the city is. I think anyone with respiratory problems already knows its a bad idea to go out when there's a bunch of smog, so I really don't see the value of the alerts as far as we are concerned. I mean, why do I need to be alerted about something I can already see with my own eyes?
I wish the media would have reported "The potential for smog is high today, so people with respiratory problems should be attentive" rather than "There's an ozone action alert, so everyone with respiratory problems is in danger" I think there's a big difference between the two, but whatever. Now I know, and I guess that's what matters.