Anax junius / Common Green Darner

Here is a set from 2011 as well, The Commn Green Darner.
From Bug Guide:

Guide images should allow for easy recognition.

- Thorax unmarked bright green in both sexes

- In mature males the abdomen has a dark purple dorsal stripe flanked by bright blue lateral stripes

- When cool, the blue stripes change to purple and may become so dark as to blend in with the dorsal stripe to give a uniform purplish abdomen (see also Internet Ref. below)

- Immature males, and females, have red abdomens and can easily be mistaken for Comet Darner

- Mature females have rusty brown to purple abdomens

Male

Female