Alrighty then, I noticed in the margin painting, you are using just one shade of blue/red, and then going in with the highlighting. If you look closely on the vertical bar of blue that comes to the right of the text in the original you will see that there is a lighter shade going along one side.

If you want to take the next step closer to period look, apply the lighter shade first, then go in with the "full" colour, sometimes there is a third darker shade as well, but not always. And lastly the highlight. It's quite simple, nearly as fast, and instantly gives the painting a tiny bit of three-dimensionality, making it pop a little more off the page. I just mix the "full" colour with a bit of white and off I go with the lighter shade.

That was the thought that struck me as I looked at your fabulous product :)