I am yet to be convinced that that light electric blue is quite right. Plus, it just hurts my eyes. My Prussian blue is darker than that (and when mixed with oil to make paint, it's darker yet). It should look nearly a dark Indigo blue (though it definitely is more "lively" with an "electric" quality).
Prussian blue as a dry pigment:
I have seen a 19th century trade gun painted black, and a 17th century English ash stocked gun painted brown. I have seen photos of one or two pre-Bess English muskets painted black also (supposedly, the natural walnut brown being the origin of the name "Brown Bess", replacing black painted ash or whatever stocks...).
Years ago, at a gunshow, I saw a Berks-ish type gun that was painted red...but I'm still not sure if it was an original gun, or something by Eric Kettenburg... It was pretty sharp.