I have a BPS in marsh grass. It came from browning like that. I am 90% sure that they use hydro transfer to get that finish on. It has been very durable.
A word of advice. Make sure the company is experienced with guns. Buddy of mine took an old auto 5 to a local guy. Looks great but he had lots of trouble getting the gun back together. and now has peeling issues due to finish being applied onto areas that shouldnt be coated.
Concentrated power is not rendered harmless by the good intentions of those who create it.