How to validate weekly card inside the Roissybus from the CDG

At the front door entrance (beside the driver) there will be a Navigo validation machine with a blue or purple circular pattern on it.  Holding your Navigo week pass card against the colored portion of the machine will emit a "ding" (good, validated) or a "buzz" (not read, try again).  See the photo on this answer to get an idea of the machine (with the purple color, the other is a paper ticket validation machine).