Structures for use in forming products having a wood grain appearance include, for example, a plurality of extruded layers having different colors/shades spirally wound about a longitudinal axis to an outer surface to define the structure. The plurality of extruded layers include varying thicknesses along a spiral length of the plurality of layers and/or portions of the plurality of extruded layers encircling the longitudinal axis include portions disposed at different distances from the longitudinal axis. In some embodiments, the spirally winding includes forming a cylindrical structure, and pressing the cylindrical structure into a cuboid structure having a square or rectangular cross-section across the longitudinal axis and at least a portion of the plurality of extruded layers defining a square or rectangle pattern across the longitudinal axis. Longitudinal portions may be cut from the structures to form the products having a wood grain appearance.