Please don't do it, more good furniture has been ruined by repainting. Nothing looks more out of place than a battlefield pickup with a shinny new stock. A tasteful field expedient repair with just the repaired areas painted or blended into the stocks current condition is the way to go, glass only, no bondo please!!!! Some Daimler - Benz browns with a heavy plumb base will be closest however in that variant pictured with the Dutch making many replacement stocks in small batches themselves there is no real "one" color depending on your stock. Which variant stock do you have, sheet fiberglass, injection molded, Dutch repro matte fiberglass?
ETA,
If the stock pictured is the one to be fixed please don't do anything to the outside. It is a rare example in good shape of a fragile part, it appears that a repair has been attempted from a look at the sling swivel hole. We are stewards of these museum pieces as they pas through time, less than ten thousand were made of all variants, this piece is very rare please be a conservator, condition is everything and unrestored is a premium that cannot be undone. Never modify original parts.
Sorry, rant off.