Bust of Sir Isaac Newton

I'm making a few little gifts for my husband, David, for his birthday which is in two weeks.  I'm planning a study/laboratory in the attic of the WAMH, which will be full of scientific instruments and so forth circa 1700.

One of the things I want in there is a bust of Sir Isaac Newton, which I picked up in England in May.  It's a 35 mm tall, solid, heavy white metal piece, sold unfinished, by Phoenix Miniatures:

I want to finish it to look like warm marble, like this 1710 bas relief of the great mathematician:

This is with two thin coats of off white artist's acrylic paint -- thin because I don't want to destroy all the detail in this piece.  This photograph of the statue has turned out too yellow because I took it at night, but the colour is actually pretty close to my reference photo.

I'll have a look at it again in the morning light, add another coat, if necessary, maybe do a gentle wash of a darker colour into the detail, and add a tiny amount of subtle veining on the base and back, where there are larger areas of "uncarved marble".