Why did you choose green glazed tiles for building roofs in Tang Dynasty?

There are several explanations. The technical problems you mentioned have been considered, because the glass craft in China was lost several times before the Sui Dynasty. Later, someone tried to reproduce the appearance of glass with green porcelain. However, as you quoted Tang Sancai as proof, this conjecture can basically be overturned.

another way of saying it is aesthetic tendency. Green, blue and other cool colors have the effect of shrinking and relaxing visually. On the basis of the overall huge building structure in the Tang Dynasty, something with a Huang Cancan on the roof will make the overall visual effect look flashy, while blue-green will precipitate the visual effect and achieve the solemn effect. In addition, there are not many architectural carvings and decorations in the Tang Dynasty, and color has become a means to reflect the architectural level and beauty. The combination of cool color and warm color makes the overall architectural effect more three-dimensional and heavy. The aesthetic requirements of the Tang dynasty changed the aesthetic standards of the previous dynasty, which were too exquisite and stressed the beauty of form, so it became what we saw.