It's the system they chose to keep things in check, I'm not aware of their inner works as I'm not their HR guy, even so color coding doesn't suggest a 'class system' (my gmail labels are color coded) it's a just a system to keep things in order.
So that humans can also read the badges without a machine. The same reason they put a picture and your name on the badge, even though the machines don't need them.
Why would they make a badge that only the computer could understand?