Thicker substrates can be created by mounting 2, 3 or more sheets together. In such an application with 3 sheets, a color seam is a center layer of paper or a layer that's wedged between two sheets that appears as a middle "seam" on the final product. They can appear in a variety of colors. Color seams are used in both our Prestige line of products and our Layer Cake products. Attached is a visual of the various colors we offer as color seams at 4OVR4.COM and the closest CMYK equivalent values to that color