White Grout Can Be Distracting

The mortar along the top of this marble tile baseboard was light colored, and I didn’t think it would look good between the black tile and the mostly-dark wallpaper.
In addition, I hate trimming wallpaper against grout, because the gritty texture makes it hard to get a neat cut. And that sandy grout sure eats up my razor blades!

So I applied a thin layer of joint compound over the grout, sanded it smooth, and then sealed with a penetrating primer called Gardz. This gave me a softer surface to trim against. But I was still left with a white edge. That’s what you see in the top photo.
So next I used an angled artist’s brush and some black craft paint from Texas Art Supply hobby store to change the white line to black.

Here’s what it looks like finished.