The outer wall of the ceramic cup is colored and the inside is white. Is drinking water poisonous?

It won't be toxic. Because the porcelain cup is made of clay, it is clean and hygienic after thousands of degrees of high temperature firing, and the inside is white. After thousands of years of use, this porcelain cup has been proved to be clean and reliable without any problems (unlike those newly invented new materials, such as nano-materials, it will take time to prove whether it is harmful). As for the color of the exterior wall, it is because the materials used are somewhat different, with a little pigment or some rare earth elements. After high-temperature barbecue and on the outer wall, it will not penetrate into the cup and drinking water will not be affected.