Yes! You can block as many revealed Event Cards as you like. But, you have to commit yourself when taking the action for how many cards you would like to block. E.g. Manuel looks at the revealed Event Cards and 4 of the 3 revealed Event Cards have a blocking area. He decides to block two of them. For the first Event Card he needs to draw a Yellow Block (as the area to block as a Yellow border) and for the second Event Card a Green Block out of the HQ Tower. He places each Block on the matching Event Card.