Basically the title. I think it's a bit odd that fire clay and red clay can be made into bricks and roofs, but blue clay can't. If that's by design because that clay is softer or something irl, I understand, but I think we could do with a few more options for decoration.
Edit: Correction. Blue Clay shingles and bricks are in the game, they just don't appear blue in the pottery menu, and are completely black once fired. I think an improvement could be made to the UI to make the shingles stand out more in the UI, as well as make the end result more of a blue-grey than a solid black.