Trev you can take a screen shot of any color and then add it as a material eg Green wet area board, we used to do what you are asking for and also add n sheet sizes but architects and interior designers did not like it. Am I reading your question correctly? I think this video will help https://youtu.be/oVmvwpDIv8M
If you want to add-in the join for say a 4' sheet or 1200 simply screen shot a rectangle that is scale and then use the material in "create material" in the wall tool. I usually do 10 materials at a time you can do 1 in less than 30 seconds once you get used to it and you will have it forever.