Okay, heres why they use the green plate and U and Ms
Corruption...if you live in IL and a FAKE leo is pulling you over, you know, that if the plate is not green and it dont have a M or U for undercover, you know its not real, and you call 911 on your cell. Or, you are using village cars for personal use, and someone can spot you, and report you to the village. for real, some time ago, I remember they had a problem with these issues and the state legislators passed laws like these to try and protect the public and the govt from illegal activity.