The old 16e century Italian masters applied a slightly tinted oil- resin layer on top of an oil varnish filler layer. Red pigment vermilion was used to give the instrument a warm red look. Due to the ultra violet light the wood gets darker when it ages.
The color changes to more dark brown over the years. The red pigments once used will fade away over the years. What stays is what we see now on most Italian Masters.
The pictures shows my Jesse van Ruller model with the bare wood all stained with a modern color pigment.
About 10 layers of nitrocellulose lacquer are used to give a smooth finish. This guitar will darken a bit more the comming few centuries.