You are on the right track though the paint is less revealing than the chemical trace yet-to-be-found on the aircraft.There is a theory that after missile break-up the remains impacted the top of the wing causing the green skid marks? This could possibly be another source of info and a possible tie up to identification of a Buk system? If it is possible I don't think that the Russians will assist with such an investiagion by providing paint samples, but other SA-11 operators would, plus the examples that the US has obtained for intelligence evaluation. (See operators at link). Possibly the investigators will find a piece of missle body within the wreckage? Are the Russian using a standard green paint that can be matched up?
This case of friendly fire from 2003 was established after copper and chemical residue were found on the landing craft that were consistent with that of a Milan missile used by British Forces in 2003.
There are databases with all known manufactured explosive chemical traces so if any are found, identification will be academic.
It is also likely that the CTs and RT will have an alternative view though....