Chalk is used in art (and scrapbooking) to add color, depth and texture. When using chalk to create the primitive look of Folk Art, the usual color choices are black and brown, in all shades. Both add an antiqued look with black providing deep shadows. When chalk is added to the edges of paper piecing, titles, journaling boxes and background paper the layout can take on an aged feel.
Try colors of chalk, that are darker than your paper color to give depth to paper edges.