All of the 77 orchard tractors I am aware of are green.  I do not know of any red ones, but custom colors were available from the factory for an additional charge, but this would seem to be rare.  I have seen many Olivers with a yellowish colored primer under the paint, and some with a reddish brown primer.  Maybe you are seeing the primer underneath the paint?  As to the C77E designation, my understanding is that a C after the serial number would designate a special transmission gear combination, with the 77 designating what gear combination.  Not sure about the E.  Hope this helps, Terry.