I don't know how bad the pollution gets in your house, but I'm willing to bet a few high-school students could do with a visual reminder that it's time to put the rubbish out. Coway's AP-1008 is that reminder.
When the hole glows red, it means the pollution is at its highest-possible level. Light purple shows it's at medium levels, purple is for low levels, and when it shows up blue you can rest easy in the knowledge the room is 99.5 per cent clean. That means the AP-1008 is doing its job adequately enough, as it is capable of removing 99.5 per cent of airborne particles.