I think the plate colors went by what ever university was up for the plate that year.The 1965 and 1967 plates were Uof M Colors.MSU was early 60s?1970 gold and white was CMU or WMU?Northern?I may be way off base on this.
You can get a "year of manufactured" plate for your classic.That is why you see old cars with 1956 plates on them for example.The plate could have been used before,it most likely was.My 1967 plate I use was new in the wrapper.On the sleeve was the codes for what county the plates were issued in.