This working memory task was developed as Experiment 1 from the 2005 study by Vogel, McCollough and Machizawa. In this task, participants are briefly shown (100ms) an array of red and blue rectangles at various angles. They are told to memorize the angles of these rectangles on a specific side of the screen. Then, after a 900ms retention interval, participants are shown a test array which may or may not be identical to the first array. If it is identical, participants should press "1" on the keyboard, if it is different, participant should press "2" on the keyboard.
To see how this experiment was made, see the video below: