There's actually a huge reason to avoid modern colorants and most painters' colors, and that is because they are almost always specifically chosen or compounded to give a lighter version of the same color when used thin, very simple colors rather than complex. One characteristic of many of the colors that violin makers in the golden period used is that they can be seen to be yellow when thin and go through orange and dark orange-brown tending towards reddish and then move towards black as they get thicker.
Modern colors start, for instance, as pink and when used thicker turn to opaque paint of some relatively light color. Often you can see this in the art store where they will put a dab of the color on a board and rub it out to thin, showing both the mass and wash colors the buyer can expect. Most stains act similarly.
This is a fundamental difference between painting and varnishing. But once in a while you can find a painter's color that does what you want. You can achieve similar but not identical results by layering starting with one color and building through the changes you want to see, but the difference is still subtly visible to someone who's looking. There's a certain amount of this happening with the golden ground (that someone above basically claimed doesn't exist :-) interacting with the colored over varnish, but that's not the whole story.
Another problem with looking at varnish is simultaneous color contrast (look it up--it's beautifully complex) which happens in the greyscale as well (that "white" you see under a new chip probably isn't as bare-assed white as you think it is). (I'll give you this one: https://www.pinterest.com/pin/409616528591130544/ )
Old violins are incredibly subtle.
By the way, the two earliest examples I have seen of a "red" Amati and a "red" Strad violate what I laid down above--both were simple colors, a red tending towards black with very little yellow component--and I have only seen a single example of each. When each maker comes back with a red color later it's quite a bit more interesting and complex, so you might think that they got it right away and found that first effort less than satisfactory. ("Well, that was interesting--I guess we won't be doing that again!")