I always figured the orange on black had something to do with Princeton, cool info regarding the other colleges as well that I was less aware of. Obviously the later and current straw/blue/buff licence plates have to do with the official state colors of buff and jersey blue.New Jersey started issuing license plates in 1908 although they go back to around 1903. At the start, they were yearly requirements and each year the plates were the colors of the state's colleges and universities. Orange and black for Princeton in 1910; dark blue and yellow for Trenton State (i.e. The College of New Jersey) in 1911. The Rutgers colors were suppose to be in 1912 but wound up Stevens' colors of red and gray. Apparently, Rutgers used scarlet with the black a lot back then. The state required at least one color to be "light" for purposes of contrast so Rutgers school colors were bypassed.
School colors were in use for large periods of the 20th century. When Brendan Bryne (Princeton '49) became Governor, he changed the license plates back to blue and orange for his alma mater.
The January 11, 1936 Targum mentioned that Edward Simpson, Rutgers ’37, had vanity plates, “He drives proudly around the campus sporting the tags marked ‘R-1937’ … the only fly in the ointment is that although lettered as Rutgers plates, they are painted orange and black, Princeton’s colors.”
According to the below links though (which I'd consider somewhat authoratative), besides 1911, NJ license plates were red on white in 1913, white on red in 1914, 20, 24, 31, and red on black in 1933. Were these RU related? I actually own a 1957 and a 1910 plate...
NJ licence plates 1930s-40s
20s and prior