I never understood the idea of the "summary picture". I guess if you see green covering everywhere you plan to be, then you don't have to think about it any more.
But the way it works is that if there will be an outage, no matter how brief, in that "square" any time during the next N hours (it defaults to 18hrs) then that square will be colored red. So if you see red there, then you have to go to "playback mode" and find out when that outage will be. It may last 5 minutes, and be finished hours before you launch. And, of course, a RAIM outage doesn't mean a GPS outage, just a lack of sufficient redundancy to be trustworthy enough for GPS approaches.
So it's the nature of that depiction to seem a bit pessimistic. But that does seem like more red than I'm used to seeing on that chart.
-harry