They just keep appearing. This is a black-tailed skimmer (Orthetrum cancellatum), gewone oeverlibel in Dutch. Young males are yellow, but get a dusty-looking blue coating (called pruinescence by biologists) when they get older:
Olympus Stylus 1s, 300mm, ISO100, f4, 1/500s
This is a female, or maybe a very young male:
Olympus Stylus 1s, 300mm, ISO200, f5.6, 1/60s
This last one got stuck in the grass. Sometimes they can't take off because there is not enough room for their wings. You can hear them trying to escape from far away; they make a very loud whirring sound. I liberated this one, of course.
Sorry about the great many photos of dragonflies. Can't help it, it is the season, you see.