Look at the color of your wood when you are shopping and buying your stain. If it is already a dark brown then the paint will likely turn out just as well. Also, if you want a really rich finish that has more than one coat (maybe even two or three) then you are going to need something darker but no matter what kind of wood you have, there will be some sort of purple tint in it because walnut itself is known for having a bit of this color.