The default behavior is to color the contour part by the creation variable. If you toggle this off, the contour part will not be colored by a variable automatically, but will be white.

Unlike most part creation operators, contours are created from the client's representation of the part - not the server's. If the parent part of the contour consists of one-dimensional elements or has no client-side visual representation at all, the resulting contour will be empty. This would be the case if the parent part was currently displayed as feature angle, border representation, or not loaded. The 3D border, 2D full representation is typically used for contour part parents. See Change the Visual Representation for more information.