Happy Birthday Flag Card for Co-Worker: Look no further for a great co-worker birthday card! You can celebrate your colleague's birthday by sending this lively and colorful birthday card. Whether for your boss, an intern or co-worker, this fun birthday card is simply perfect and does the trick. It's stylish and simple with a bright, lime green background and funky happy birthday banner. Let them know you are happy to work alongside them, and send wishes for a great year!